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id="toc-Liquid-driven_escapements" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Liquid-driven_escapements"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Liquid-driven escapements</span> </div> </a> <ul id="toc-Liquid-driven_escapements-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Mechanical_escapements" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Mechanical_escapements"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Mechanical escapements</span> </div> </a> <ul id="toc-Mechanical_escapements-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Reliability" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Reliability"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Reliability</span> </div> </a> <ul id="toc-Reliability-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Accuracy" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Accuracy"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Accuracy</span> </div> </a> <ul id="toc-Accuracy-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Mechanical_escapements_2" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Mechanical_escapements_2"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Mechanical escapements</span> </div> </a> <button aria-controls="toc-Mechanical_escapements_2-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Mechanical escapements subsection</span> </button> <ul id="toc-Mechanical_escapements_2-sublist" class="vector-toc-list"> <li id="toc-Verge_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Verge_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Verge escapement</span> </div> </a> <ul id="toc-Verge_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cross-beat_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cross-beat_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Cross-beat escapement</span> </div> </a> <ul id="toc-Cross-beat_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Galileo's_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Galileo's_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Galileo's escapement</span> </div> </a> <ul id="toc-Galileo's_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Anchor_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Anchor_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.4</span> <span>Anchor escapement</span> </div> </a> <ul id="toc-Anchor_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Deadbeat_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Deadbeat_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5</span> <span>Deadbeat escapement</span> </div> </a> <ul id="toc-Deadbeat_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Pin_wheel_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Pin_wheel_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.6</span> <span>Pin wheel escapement</span> </div> </a> <ul id="toc-Pin_wheel_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Detent_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Detent_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.7</span> <span>Detent escapement</span> </div> </a> <ul id="toc-Detent_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cylinder_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cylinder_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.8</span> <span>Cylinder escapement</span> </div> </a> <ul id="toc-Cylinder_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Duplex_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Duplex_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.9</span> <span>Duplex escapement</span> </div> </a> <ul id="toc-Duplex_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Lever_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Lever_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.10</span> <span>Lever escapement</span> </div> </a> <ul id="toc-Lever_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Grasshopper_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Grasshopper_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.11</span> <span>Grasshopper escapement</span> </div> </a> <ul id="toc-Grasshopper_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Gravity_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Gravity_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.12</span> <span>Gravity escapement</span> </div> </a> <ul id="toc-Gravity_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Coaxial_escapement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Coaxial_escapement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.13</span> <span>Coaxial escapement</span> </div> </a> <ul id="toc-Coaxial_escapement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Other_modern_watch_escapements" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Other_modern_watch_escapements"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.14</span> <span>Other modern watch escapements</span> </div> </a> <ul id="toc-Other_modern_watch_escapements-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Electromechanical_escapements" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Electromechanical_escapements"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Electromechanical escapements</span> </div> </a> <button aria-controls="toc-Electromechanical_escapements-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Electromechanical escapements subsection</span> </button> <ul id="toc-Electromechanical_escapements-sublist" class="vector-toc-list"> <li id="toc-Hipp_clock" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Hipp_clock"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Hipp clock</span> </div> </a> <ul id="toc-Hipp_clock-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Synchronome_switch" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Synchronome_switch"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Synchronome switch</span> </div> </a> <ul id="toc-Synchronome_switch-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Free_pendulum_clock" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Free_pendulum_clock"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Free pendulum clock</span> </div> </a> <ul id="toc-Free_pendulum_clock-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Citations" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Citations"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Citations</span> </div> </a> <ul id="toc-Citations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div 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mw-first-heading"><span class="mw-page-title-main">Escapement</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 27 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-27" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">27 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%85%D9%8A%D8%B2%D8%A7%D9%86_%D8%A7%D9%84%D8%B3%D8%A7%D8%B9%D8%A9" title="ميزان الساعة – Arabic" lang="ar" hreflang="ar" data-title="ميزان الساعة" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Escapament" title="Escapament – Catalan" lang="ca" hreflang="ca" data-title="Escapament" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Gollyngiad" title="Gollyngiad – Welsh" lang="cy" hreflang="cy" data-title="Gollyngiad" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/H%C3%A6mv%C3%A6rk" title="Hæmværk – Danish" lang="da" hreflang="da" data-title="Hæmværk" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Hemmung_(Uhr)" title="Hemmung (Uhr) – German" lang="de" hreflang="de" data-title="Hemmung (Uhr)" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Mecanismo_de_escape" title="Mecanismo de escape – Spanish" lang="es" hreflang="es" data-title="Mecanismo de escape" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Ellaso" title="Ellaso – Esperanto" lang="eo" hreflang="eo" data-title="Ellaso" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%DA%86%D8%B1%D8%AE%E2%80%8C%D8%AF%D9%86%DA%AF" title="چرخ‌دنگ – Persian" lang="fa" hreflang="fa" data-title="چرخ‌دنگ" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/%C3%89chappement_(horlogerie)" title="Échappement (horlogerie) – French" lang="fr" hreflang="fr" data-title="Échappement (horlogerie)" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%83%88%EC%A7%84%EA%B8%B0" title="탈진기 – Korean" lang="ko" hreflang="ko" data-title="탈진기" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AE%E0%A5%8B%E0%A4%9A%E0%A4%A8" title="मोचन – Hindi" lang="hi" hreflang="hi" data-title="मोचन" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Zup%C4%8Dasti_prekida%C4%8D" title="Zupčasti prekidač – Croatian" lang="hr" hreflang="hr" data-title="Zupčasti prekidač" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Escapement" title="Escapement – Indonesian" lang="id" hreflang="id" data-title="Escapement" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Scappamento" title="Scappamento – Italian" lang="it" hreflang="it" data-title="Scappamento" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Bolosan" title="Bolosan – Malay" lang="ms" hreflang="ms" data-title="Bolosan" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/%D0%A2%D1%8D%D1%8D%D0%B3%D0%BB%D2%AF%D2%AF%D1%80_(%D0%A6%D0%B0%D0%B3)" title="Тээглүүр (Цаг) – Mongolian" lang="mn" hreflang="mn" data-title="Тээглүүр (Цаг)" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Echappement_(uurwerk)" title="Echappement (uurwerk) – Dutch" lang="nl" hreflang="nl" data-title="Echappement (uurwerk)" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E8%84%B1%E9%80%B2%E6%A9%9F" title="脱進機 – Japanese" lang="ja" hreflang="ja" data-title="脱進機" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Hemverk" title="Hemverk – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Hemverk" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Escapament_(relotjari%C3%A1)" title="Escapament (relotjariá) – Occitan" lang="oc" hreflang="oc" data-title="Escapament (relotjariá)" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Wychwyt" title="Wychwyt – Polish" lang="pl" hreflang="pl" data-title="Wychwyt" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A1%D0%BF%D1%83%D1%81%D0%BA%D0%BE%D0%B2%D0%BE%D0%B9_%D0%BC%D0%B5%D1%85%D0%B0%D0%BD%D0%B8%D0%B7%D0%BC_%D1%87%D0%B0%D1%81%D0%BE%D0%B2" title="Спусковой механизм часов – Russian" lang="ru" hreflang="ru" data-title="Спусковой механизм часов" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Zapinja%C4%8Da" title="Zapinjača – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Zapinjača" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/E%C5%9Fapman" title="Eşapman – Turkish" lang="tr" hreflang="tr" data-title="Eşapman" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%A1%D0%BF%D1%83%D1%81%D0%BA%D0%BE%D0%B2%D0%B8%D0%B9_%D0%BC%D0%B5%D1%85%D0%B0%D0%BD%D1%96%D0%B7%D0%BC_%D0%B3%D0%BE%D0%B4%D0%B8%D0%BD%D0%BD%D0%B8%D0%BA%D0%B0" title="Спусковий механізм годинника – Ukrainian" lang="uk" hreflang="uk" data-title="Спусковий механізм годинника" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%DB%81%D8%B1%D9%88%D8%A8" title="ہروب – Urdu" lang="ur" hreflang="ur" data-title="ہروب" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E6%93%92%E7%BA%B5%E5%99%A8" title="擒纵器 – Chinese" lang="zh" hreflang="zh" data-title="擒纵器" data-language-autonym="中文" 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class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Mechanism for regulating the speed of clocks</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">For other uses, see <a href="/wiki/Escapement_(disambiguation)" class="mw-disambig" title="Escapement (disambiguation)">Escapement (disambiguation)</a>.</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Anchor_escapement_animation_217x328px.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/2/29/Anchor_escapement_animation_217x328px.gif" decoding="async" width="217" height="328" class="mw-file-element" data-file-width="217" data-file-height="328" /></a><figcaption>Animation of an <a href="/wiki/Anchor_escapement" title="Anchor escapement">anchor escapement</a>, widely used in <a href="/wiki/Pendulum_clock" title="Pendulum clock">pendulum clocks</a></figcaption></figure> <p>An <b>escapement</b> is a <a href="/wiki/Mechanical_linkage" class="mw-redirect" title="Mechanical linkage">mechanical linkage</a> in <a href="/wiki/Mechanical_watch" title="Mechanical watch">mechanical watches</a> and <a href="/wiki/Clock" title="Clock">clocks</a> that gives impulses to the timekeeping element and periodically releases the <a href="/wiki/Gear_train" title="Gear train">gear train</a> to move forward, advancing the clock's hands. The impulse action transfers energy to the clock's timekeeping element (usually a <a href="/wiki/Pendulum" title="Pendulum">pendulum</a> or <a href="/wiki/Balance_wheel" title="Balance wheel">balance wheel</a>) to replace the energy lost to friction during its cycle and keep the timekeeper oscillating. The escapement is driven by force from a coiled <a href="/wiki/Spring_(device)" title="Spring (device)">spring</a> or a suspended weight, transmitted through the timepiece's gear train. Each swing of the pendulum or balance wheel releases a tooth of the escapement's <i>escape wheel</i>, allowing the clock's gear train to advance or "escape" by a fixed amount. This regular periodic advancement moves the clock's hands forward at a steady rate. At the same time, the tooth gives the timekeeping element a push, before another tooth catches on the escapement's pallet, returning the escapement to its "locked" state. The sudden stopping of the escapement's tooth is what generates the characteristic "ticking" sound heard in operating mechanical clocks and watches. </p><p>The first mechanical escapement, the <a href="/wiki/Verge_escapement" title="Verge escapement">verge escapement</a>, was invented in <a href="/wiki/Medieval_Europe" class="mw-redirect" title="Medieval Europe">medieval Europe</a> during the 13th century and was the crucial innovation that led to the development of the mechanical clock. The design of the escapement has a large effect on a timepiece's accuracy, and improvements in escapement design drove improvements in time measurement during the era of mechanical timekeeping from the 13th through the 19th century. </p><p>Escapements are also used in other mechanisms besides timepieces. Manual typewriters used escapements to step the carriage as each letter (or space) was typed. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=1" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The invention of the escapement was an important step in the <a href="/wiki/History_of_technology" title="History of technology">history of technology</a>, as it made the all-mechanical clock possible.<sup id="cite_ref-Marrison_1-0" class="reference"><a href="#cite_note-Marrison-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page / location: p.514-515">: p.514-515 </span></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Cipolla_3-0" class="reference"><a href="#cite_note-Cipolla-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The first all-mechanical escapement, the <a href="/wiki/Verge_escapement" title="Verge escapement">verge escapement</a>, was invented in 13th-century Europe. It allowed timekeeping methods to move from continuous processes such as the flow of water in <a href="/wiki/Water_clock" title="Water clock">water clocks</a>, to repetitive <a href="/wiki/Oscillatory" class="mw-redirect" title="Oscillatory">oscillatory</a> processes such as the swing of <a href="/wiki/Pendulum" title="Pendulum">pendulums</a>, enabling more accurate timekeeping.<sup id="cite_ref-Cipolla_3-1" class="reference"><a href="#cite_note-Cipolla-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Oscillating timekeepers are the controlling devices in all modern clocks.<sup id="cite_ref-Jesperson_4-0" class="reference"><a href="#cite_note-Jesperson-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Bloomfield_5-0" class="reference"><a href="#cite_note-Bloomfield-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-NIST1_6-0" class="reference"><a href="#cite_note-NIST1-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Liquid-driven_escapements">Liquid-driven escapements</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=2" title="Edit section: Liquid-driven escapements"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The earliest liquid-driven escapement was described by the <a href="/wiki/Ancient_Greece" title="Ancient Greece">Greek</a> engineer <a href="/wiki/Philo_of_Byzantium" title="Philo of Byzantium">Philo of Byzantium</a> in the 3rd century BC in chapter 31 of his technical treatise <i>Pneumatics</i>, as part of a <a href="/wiki/Washstand" title="Washstand">washstand</a>.<sup id="cite_ref-Lewis_2000_356f._7-0" class="reference"><a href="#cite_note-Lewis_2000_356f.-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> A <a href="/wiki/Counterweight" title="Counterweight">counterweighted</a> spoon, supplied by a water tank, tips over in a basin when full, releasing a spherical piece of <a href="/wiki/Pumice" title="Pumice">pumice</a> in the process. Once the spoon has emptied, it is pulled up again by the counterweight, closing the door on the pumice by the tightening string. Remarkably, Philo's comment that "its construction is similar to that of clocks" indicates that such escapement mechanisms were already integrated in ancient water clocks.<sup id="cite_ref-Lewis_2000_356f._7-1" class="reference"><a href="#cite_note-Lewis_2000_356f.-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>In China, the <a href="/wiki/Tang_dynasty" title="Tang dynasty">Tang dynasty</a> Buddhist monk <a href="/wiki/Yi_Xing" title="Yi Xing">Yi Xing</a>, along with government official <a href="/wiki/Liang_Lingzan" title="Liang Lingzan">Liang Lingzan</a>, made in 723 (or 725) AD the escapement for the workings of a water-powered <a href="/wiki/Armillary_sphere" title="Armillary sphere">armillary sphere</a> and <a href="/wiki/Drive_wheel" title="Drive wheel">clock drive</a>, which was the world's first clockwork escapement.<sup id="cite_ref-needham_volume_4_part_2_165_8-0" class="reference"><a href="#cite_note-needham_volume_4_part_2_165-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Song_dynasty" title="Song dynasty">Song dynasty</a> horologists <a href="/wiki/Zhang_Sixun" title="Zhang Sixun">Zhang Sixun</a> and <a href="/wiki/Su_Song" title="Su Song">Su Song</a> duly applied escapement devices for their <a href="/wiki/Astronomical_clock" title="Astronomical clock">astronomical clock towers</a> in the 10th century,<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> where water flowed into a container on a pivot. However, the technology later stagnated and retrogressed. According to historian <a href="/wiki/Derek_J._de_Solla_Price" title="Derek J. de Solla Price">Derek J. de Solla Price</a>, the Chinese escapement spread west and was the source of Western escapement technology.<sup id="cite_ref-Derek_11-0" class="reference"><a href="#cite_note-Derek-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>According to <a href="/wiki/Ahmad_Y._Hassan" class="mw-redirect" title="Ahmad Y. Hassan">Ahmad Y. Hassan</a>, a <a href="/wiki/Mercury_(element)" title="Mercury (element)">mercury</a> escapement described in a <a href="/wiki/Spanish_language" title="Spanish language">Spanish</a> document for <a href="/wiki/Alfonso_X" class="mw-redirect" title="Alfonso X">Alfonso X</a> in 1277 can be traced to earlier <a href="/wiki/Arabic_language" class="mw-redirect" title="Arabic language">Arabic</a> sources.<sup id="cite_ref-Hassan_12-0" class="reference"><a href="#cite_note-Hassan-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Reliable_sources" title="Wikipedia:Reliable sources"><span title="The material near this tag may rely on an unreliable source. (September 2010)">unreliable source?</span></a></i>]</sup> Knowledge of these mercury escapements may have spread through Europe with translations of Arabic and Spanish texts.<sup id="cite_ref-Hassan_12-1" class="reference"><a href="#cite_note-Hassan-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Ajram_13-0" class="reference"><a href="#cite_note-Ajram-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>However, none of these were true mechanical escapements, since they still depended on the flow of liquid through a hole to measure time. In these designs, a container tipped over each time it filled up, thus advancing the clock's wheels each time an equal quantity of water was measured out. The time between releases depended on the rate of flow, as do all liquid clocks. The rate of flow of a liquid through a hole varies with temperature and viscosity changes and decreases with pressure as the level of liquid in the source container drops. The development of mechanical clocks depended on the invention of an escapement which would allow a clock's movement to be controlled by an oscillating weight, which would stay constant. </p> <div class="mw-heading mw-heading3"><h3 id="Mechanical_escapements">Mechanical escapements</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=3" title="Edit section: Mechanical escapements"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The first mechanical escapement, the <a href="/wiki/Verge_escapement" title="Verge escapement">verge escapement</a>, was used in a bell-ringing apparatus called an <span title="Latin-language text"><i lang="la">alarum</i></span> for several centuries before it was adapted to clocks.<sup id="cite_ref-Headrick_14-0" class="reference"><a href="#cite_note-Headrick-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> Some sources claim that French architect <a href="/wiki/Villard_de_Honnecourt" title="Villard de Honnecourt">Villard de Honnecourt</a> invented the first escapement in 1237, citing a drawing of a rope linkage to turn a statue of an angel to follow the sun, found in his notebooks;<sup id="cite_ref-Usher_15-0" class="reference"><a href="#cite_note-Usher-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> however, the consensus is that this was not an escapement.<sup id="cite_ref-Scheller_16-0" class="reference"><a href="#cite_note-Scheller-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Barnes_17-0" class="reference"><a href="#cite_note-Barnes-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Wang_18-0" class="reference"><a href="#cite_note-Wang-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Needham_19-0" class="reference"><a href="#cite_note-Needham-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-White_20-0" class="reference"><a href="#cite_note-White-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Rossum_21-0" class="reference"><a href="#cite_note-Rossum-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>Astronomer <a href="/wiki/Robertus_Anglicus" title="Robertus Anglicus">Robertus Anglicus</a> wrote in 1271 that <a href="/wiki/Clockmaker" title="Clockmaker">clockmakers</a> were trying to invent an escapement, but had not yet been successful.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Records in financial transactions for the construction of clocks point to the late 13th century as the most likely date for when tower clock mechanisms transitioned from water clocks to mechanical escapements.<sup id="cite_ref-Whitrow_23-0" class="reference"><a href="#cite_note-Whitrow-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 103-104">: 103-104 </span></sup><sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> Most sources agree that mechanical escapement clocks existed by 1300.<sup id="cite_ref-Cipolla2004_25-0" class="reference"><a href="#cite_note-Cipolla2004-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p><p>However, the earliest available description of an escapement was not a verge escapement, but a variation called a <i>strob</i> escapement. Described in <a href="/wiki/Richard_of_Wallingford" title="Richard of Wallingford">Richard of Wallingford</a>'s 1327 manuscript <span title="Latin-language text"><i lang="la">Tractatus Horologii Astronomici</i></span> on the clock that he built at the <a href="/wiki/Abbey_of_St._Albans" class="mw-redirect" title="Abbey of St. Albans">Abbey of St. Albans</a>, this escapement consisted of a pair of escape wheels on the same axle, with alternating radial teeth. The verge rod was suspended between them, with a short crosspiece that rotated first in one direction and then the other as the staggered teeth pushed past.<sup id="cite_ref-Whitrow_23-1" class="reference"><a href="#cite_note-Whitrow-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 103-104">: 103-104 </span></sup> Although no other example is known, it is possible that this was the first clock escapement design.<sup id="cite_ref-Whitrow_23-2" class="reference"><a href="#cite_note-Whitrow-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 103-104">: 103-104 </span></sup><sup id="cite_ref-North2_27-0" class="reference"><a href="#cite_note-North2-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </p><p>The verge became the standard escapement used in all other early clocks and watches, and remained the only known escapement for 400 years. Its performance was limited by friction and recoil, but most importantly, the early <a href="/wiki/Balance_wheel" title="Balance wheel">balance wheels</a> used in verge escapements, known as the <i>foliot</i>, lacked a <a href="/wiki/Balance_spring" title="Balance spring">balance spring</a> and thus had no natural "beat", severely limiting their timekeeping accuracy.<sup id="cite_ref-Marrison_1-1" class="reference"><a href="#cite_note-Marrison-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page / location: p.514-515">: p.514-515 </span></sup><sup id="cite_ref-Headrick_14-1" class="reference"><a href="#cite_note-Headrick-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-NIST2_29-0" class="reference"><a href="#cite_note-NIST2-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Whitrow_23-3" class="reference"><a href="#cite_note-Whitrow-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 124-125">: 124-125 </span></sup> </p><p>A great leap in the accuracy of escapements happened after 1657, due to the invention of the pendulum and the addition of the balance spring to the balance wheel,<sup id="cite_ref-NIST2_29-1" class="reference"><a href="#cite_note-NIST2-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Headrick_14-2" class="reference"><a href="#cite_note-Headrick-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Whitrow_23-4" class="reference"><a href="#cite_note-Whitrow-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 124-125">: 124-125 </span></sup> which made the timekeepers in both clocks and watches <a href="/wiki/Harmonic_oscillator" title="Harmonic oscillator">harmonic oscillators</a>. The resulting improvement in timekeeping accuracy enabled greater focus on the accuracy of the escapement. The next two centuries, the "golden age" of mechanical <a href="/wiki/Horology" class="mw-redirect" title="Horology">horology</a>, saw the invention of over 300 escapement designs, although only about ten of these were ever widely used in clocks and watches.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p><p>The invention of the <a href="/wiki/Crystal_oscillator" title="Crystal oscillator">crystal oscillator</a> and the <a href="/wiki/Quartz_clock" title="Quartz clock">quartz clock</a> in the 1920s, which became the most accurate clock by the 1930s, shifted technological research in timekeeping to <a href="/wiki/Electronics" title="Electronics">electronic</a> methods, and escapement design ceased to play a role in advancing timekeeping precision. </p> <div class="mw-heading mw-heading2"><h2 id="Reliability">Reliability</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=4" title="Edit section: Reliability"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The reliability of an escapement depends on the quality of workmanship and the level of maintenance given. A poorly constructed or poorly maintained escapement will cause problems. The escapement must accurately convert the oscillations of the pendulum or balance wheel into rotation of the clock or watch gear train, and it must deliver enough energy to the pendulum or balance wheel to maintain its oscillation. </p><p>In many escapements, the unlocking of the escapement involves sliding motion; for example, in the animation shown above, the pallets of the anchor slide against the escapement wheel teeth as the pendulum swings. The pallets are often made of very hard materials such as polished stone (for example, artificial ruby), but even so, they normally require lubrication. Since lubricating oil degrades over time due to evaporation, dust, and oxidation, periodic re-lubrication is needed. If this is not done, the timepiece may work unreliably or stop altogether, and the escapement components may be subjected to rapid wear. The increased reliability of modern watches is due primarily to the higher-quality oils used for lubrication. Lubricant lifetimes can be greater than five years in a high-quality watch. </p><p>Some escapements avoid sliding friction, such as the <a href="/wiki/Grasshopper_escapement" title="Grasshopper escapement">grasshopper escapement</a> of <a href="/wiki/John_Harrison" title="John Harrison">John Harrison</a> in the 18th century. These designs may avoid the need for lubrication in the escapement (though it does not obviate the requirement for lubrication of other parts of the gear train). </p> <div class="mw-heading mw-heading2"><h2 id="Accuracy">Accuracy</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=5" title="Edit section: Accuracy"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The accuracy of a mechanical clock is dependent on the accuracy of the timing device. If this is a pendulum, then the <a href="/wiki/Pendulum#Period_of_oscillation" title="Pendulum">pendulum's period</a> of swing determines the accuracy. If the pendulum rod is made of metal, it will expand and contract with heat, lengthening or shortening the pendulum; this changes the time taken for a swing. Special alloys are used in expensive pendulum-based clocks to minimize this distortion. The degrees of arc in which a pendulum may swing varies; highly accurate pendulum-based clocks have very small arcs in order to minimize the <a href="/wiki/Pendulum#Period_of_oscillation" title="Pendulum">circular error</a>. </p><p>Pendulum-based clocks can achieve outstanding accuracy. Even into the 20th century, pendulum-based clocks were reference timepieces in laboratories. </p><p>Escapements play a big part in accuracy as well. The precise point in the pendulum's travel at which impulse is supplied will affect how closely to time the pendulum will swing. Ideally, the impulse should be evenly distributed on either side of the lowest point of the pendulum's swing. This is called "being in beat." This is because pushing a pendulum when it is moving towards mid-swing makes it gain, whereas pushing it while it is moving away from mid-swing makes it lose. If the impulse is evenly distributed then it gives energy to the pendulum without changing the time of its swing.<sup id="cite_ref-Rawlings_31-0" class="reference"><a href="#cite_note-Rawlings-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p><p>The pendulum's period depends slightly on the size of the swing. If the amplitude changes from 4° to 3°, the period of the pendulum will decrease by about 0.013 percent, which translates into a gain of about 12 seconds per day. This is caused by the restoring force on the pendulum being circular not linear; thus, the period of the pendulum is only approximately linear in the regime of the <a href="/wiki/Small_angle_approximation" class="mw-redirect" title="Small angle approximation">small angle approximation</a>. To be time-independent, the path must be <a href="/wiki/Cycloid#Cycloidal_pendulum" title="Cycloid">cycloidal</a>. To minimize the effect with amplitude, pendulum swings are kept as small as possible. </p><p>As a rule, whatever the method of impulse, the action of the escapement should have the smallest effect on the oscillator that can be achieved. This effect, which all escapements have to a larger or smaller degree, is known as the <i>escapement error</i>. </p><p>Any escapement with sliding friction will need lubrication, but as this deteriorates the friction will increase, and, perhaps, insufficient power will be transferred to the timing device. If the timing device is a pendulum, the increased frictional forces will decrease the <a href="/wiki/Q_factor" title="Q factor">Q factor</a>, increasing the resonance band, and decreasing its precision. For spring-driven clocks, the impulse force applied by the spring changes as the spring is unwound, following <a href="/wiki/Hooke%27s_law" title="Hooke's law">Hooke's law</a>. For gravity-driven clocks, the impulse force also increases as the driving weight falls and more chain suspends the weight from the gear train; in practice, however, this effect is only seen in large public clocks, and it can be avoided by a closed-loop chain. </p><p>Watches and smaller clocks do not use pendulums as the timing device. Instead, they use a <a href="/wiki/Balance_spring" title="Balance spring">balance spring</a>: a fine spring connected to a metal <a href="/wiki/Balance_wheel" title="Balance wheel">balance wheel</a> that oscillates (rotates back and forth). Most modern mechanical watches have a working frequency of 3–4 <a href="/wiki/Hertz" title="Hertz">Hz</a> (oscillations per second) or 6–8 beats per second (21,600–28,800 beats per hour; bph). Faster or slower speeds are used in some watches (33,600<span class="nowrap"> </span>bph, or 19,800<span class="nowrap"> </span>bph). The working frequency depends on the balance spring's stiffness (<a href="/wiki/Spring_constant" class="mw-redirect" title="Spring constant">spring constant</a>); to keep time, the stiffness should not vary with temperature. Consequently, balance springs use sophisticated alloys; in this area, watchmaking is still advancing. As with the pendulum, the escapement must provide a small kick each cycle to keep the balance wheel oscillating. Also, the same lubrication problem occurs over time; the watch will lose accuracy (typically it will speed up) when the escapement lubrication starts to fail.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (June 2016)">citation needed</span></a></i>]</sup> </p><p>Pocket watches were the predecessor of modern wristwatches. Pocket watches, being in the pocket, were usually in a vertical orientation. Gravity causes some loss of accuracy as it magnifies over time any lack of symmetry in the weight of the balance. The <i><a href="/wiki/Tourbillon" title="Tourbillon">tourbillon</a></i> was invented to minimize this: the balance and spring are put in a cage that rotates (typically but not necessarily, once a minute), smoothing gravitational distortions. This very clever and sophisticated clockwork is a prized <a href="/wiki/Complication_(horology)" title="Complication (horology)">complication</a> in wristwatches, even though the natural movement of the wearer tends to smooth gravitational influences anyway. </p><p>The most accurate commercially produced mechanical clock was the <a href="/wiki/Electromechanical" class="mw-redirect" title="Electromechanical">electromechanical</a> <a href="/wiki/Shortt-synchronome_clock" class="mw-redirect" title="Shortt-synchronome clock">Shortt-Synchronome free pendulum clock</a> invented by W. H. Shortt in 1921, which had an uncertainty of about 1 second per year.<sup id="cite_ref-Jones2000_32-0" class="reference"><a href="#cite_note-Jones2000-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> The most accurate mechanical clock to date is probably the <a href="/wiki/Electromechanical" class="mw-redirect" title="Electromechanical">electromechanical</a> Littlemore Clock, built by noted archaeologist <a href="/wiki/Edward_Thomas_Hall" class="mw-redirect" title="Edward Thomas Hall">E. T. Hall</a> in the 1990s. In Hall's paper,<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> he reports an uncertainty of 3 parts in 10<sup>9</sup> measured over 100 days (an uncertainty of about 0.02 seconds over that period). Both of these clocks are <a href="/wiki/Electromechanical" class="mw-redirect" title="Electromechanical">electromechanical</a> clocks: they use a pendulum as the timekeeping element, but electrical power rather than a mechanical gear train to supply energy to the pendulum. </p> <div class="mw-heading mw-heading2"><h2 id="Mechanical_escapements_2">Mechanical escapements</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=6" title="Edit section: Mechanical escapements"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-Original_research plainlinks metadata ambox ambox-content ambox-Original_research" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/40px-Ambox_important.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/60px-Ambox_important.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/80px-Ambox_important.svg.png 2x" data-file-width="40" data-file-height="40" /></span></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>possibly contains <a href="/wiki/Wikipedia:No_original_research" title="Wikipedia:No original research">original research</a></b>.<span class="hide-when-compact"> Please <a class="external text" href="https://en.wikipedia.org/w/index.php?title=Escapement&action=edit">improve it</a> by <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verifying</a> the claims made and adding <a href="/wiki/Wikipedia:Citing_sources#Inline_citations" title="Wikipedia:Citing sources">inline citations</a>. Statements consisting only of original research should be removed.</span> <span class="date-container"><i>(<span class="date">May 2019</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>Since 1658 when the introduction of the <a href="/wiki/Pendulum" title="Pendulum">pendulum</a> and <a href="/wiki/Balance_spring" title="Balance spring">balance spring</a> made accurate timepieces possible, it has been estimated that more than three hundred different mechanical escapements have been devised, but only about 10 have seen widespread use.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> These are described below. In the 20th century, electric timekeeping methods replaced mechanical clocks and watches, so escapement design became a little-known curiosity. </p> <div class="mw-heading mw-heading3"><h3 id="Verge_escapement">Verge escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=7" title="Edit section: Verge escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Verge_escapement" title="Verge escapement">Verge escapement</a></div> <style data-mw-deduplicate="TemplateStyles:r1273380762/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:392px;max-width:392px"><div class="trow"><div class="tsingle" style="width:193px;max-width:193px"><div class="thumbimage" style="height:188px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Verge_Escapement_Labelled.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a3/Verge_Escapement_Labelled.png/191px-Verge_Escapement_Labelled.png" decoding="async" width="191" height="188" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a3/Verge_Escapement_Labelled.png/287px-Verge_Escapement_Labelled.png 1.5x, //upload.wikimedia.org/wikipedia/commons/a/a3/Verge_Escapement_Labelled.png 2x" data-file-width="373" data-file-height="368" /></a></span></div><div class="thumbcaption">Verge escapement showing crown wheel (c), verge rod (v), and pallets (p,q). Orientation is shown for use with a pendulum. When used with a foliot, the wheel and rod are vertical.</div></div><div class="tsingle" style="width:195px;max-width:195px"><div class="thumbimage" style="height:188px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Verge_and_foliot_from_De_Vick%27s_clock.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Verge_and_foliot_from_De_Vick%27s_clock.svg/193px-Verge_and_foliot_from_De_Vick%27s_clock.svg.png" decoding="async" width="193" height="189" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Verge_and_foliot_from_De_Vick%27s_clock.svg/290px-Verge_and_foliot_from_De_Vick%27s_clock.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Verge_and_foliot_from_De_Vick%27s_clock.svg/386px-Verge_and_foliot_from_De_Vick%27s_clock.svg.png 2x" data-file-width="1268" data-file-height="1243" /></a></span></div><div class="thumbcaption">Verge and foliot of De Vick clock, built 1379, Paris</div></div></div></div></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:VergeEscapementCycle.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/7/7f/VergeEscapementCycle.gif" decoding="async" width="200" height="200" class="mw-file-element" data-file-width="200" data-file-height="200" /></a><figcaption>Animation of a verge escapement</figcaption></figure> <p>The earliest mechanical escapement, from the late 1200s,<sup id="cite_ref-Rossum_21-1" class="reference"><a href="#cite_note-Rossum-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Whitrow_23-5" class="reference"><a href="#cite_note-Whitrow-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 105">: 105 </span></sup> was the <a href="/wiki/Verge_escapement" title="Verge escapement">verge escapement</a>, also known as the crown-wheel escapement. It was used in the first mechanical clocks and was originally controlled by a <a href="/wiki/Balance_wheel" title="Balance wheel">foliot</a>, a horizontal bar with weights at either end. The escapement consists of an escape wheel shaped somewhat like a crown, with pointed teeth sticking axially out of the side, oriented horizontally. In front of the crown wheel is a vertical shaft, attached to the foliot at the top, which carries two metal plates (pallets) sticking out like flags from a flag pole, oriented about ninety degrees apart, so only one engages the crown wheel teeth at a time. As the wheel turns, one tooth pushes against the upper pallet, rotating the shaft and the attached foliot. As the tooth pushes past the upper pallet, the lower pallet swings into the path of the teeth on the other side of the wheel. A tooth catches on the lower pallet, rotating the shaft back the other way, and the cycle repeats. A disadvantage of the escapement was that each time a tooth landed on a pallet, the momentum of the foliot pushed the crown wheel backward a short distance before the force of the wheel reversed the motion. This is called <i>recoil</i> and was a source of wear and inaccuracy. </p><p>The verge was the only escapement used in clocks and watches for 350 years. In spring-driven clocks and watches, it required a <a href="/wiki/Fusee_(horology)" title="Fusee (horology)">fusee</a> to even out the force of the <a href="/wiki/Mainspring" title="Mainspring">mainspring</a>. It was used in the first pendulum clocks for about 50 years after the pendulum clock was invented in 1656. In a pendulum clock, the crown wheel and staff were oriented horizontally, and the pendulum was hung from the staff. However, the verge is the most inaccurate of the common escapements, and after the pendulum was introduced in the 1650s, the verge began to be replaced by other escapements, being abandoned only by the late 1800s. By this time, the fashion for thin watches had required that the escape wheel be made very small, amplifying the effects of wear, and when a watch of this period is wound up today, it will often be found to run very fast, gaining many hours per day. </p> <div class="mw-heading mw-heading3"><h3 id="Cross-beat_escapement">Cross-beat escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=8" title="Edit section: Cross-beat escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 1584 <a href="/wiki/Jost_B%C3%BCrgi" title="Jost Bürgi">Jost Bürgi</a> invented the cross-beat escapement, a variation of the <a href="#Verge_escapement">verge escapement</a> that had two foliots that rotated in opposite directions.<sup id="cite_ref-Day_36-0" class="reference"><a href="#cite_note-Day-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> According to contemporary accounts, his clocks achieved remarkable accuracy of within a minute per day,<sup id="cite_ref-Day_36-1" class="reference"><a href="#cite_note-Day-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> two orders of magnitude better than other clocks of the time. However, this improvement was probably not due to the escapement itself, but rather to better workmanship and his invention of the <a href="/wiki/Remontoire" title="Remontoire">remontoire</a>, a device that isolated the escapement from changes in drive force.<sup id="cite_ref-Day_36-2" class="reference"><a href="#cite_note-Day-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> Without a balance spring, the cross-beat would have been no more isochronous than the verge.<sup id="cite_ref-Day_36-3" class="reference"><a href="#cite_note-Day-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Galileo's_escapement"><span id="Galileo.27s_escapement"></span>Galileo's escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=9" title="Edit section: Galileo's escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Galileo%27s_escapement" title="Galileo's escapement">Galileo's escapement</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Galileo_Pendulum_Clock.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Galileo_Pendulum_Clock.jpg/150px-Galileo_Pendulum_Clock.jpg" decoding="async" width="150" height="241" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Galileo_Pendulum_Clock.jpg/225px-Galileo_Pendulum_Clock.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/8/8c/Galileo_Pendulum_Clock.jpg 2x" data-file-width="250" data-file-height="401" /></a><figcaption>Original drawing (<abbr title="circa">c.</abbr><span style="white-space:nowrap;"> 1637</span>) of Galileo's pendulum clock and escapement</figcaption></figure><p> Galileo's escapement is a design for a clock escapement, invented around 1637 by Italian scientist <a href="/wiki/Galileo_Galilei" title="Galileo Galilei">Galileo Galilei</a>. It was the earliest design of a <a href="/wiki/Pendulum_clock" title="Pendulum clock">pendulum clock</a>. Since he was blind by then, Galileo described the device to his <a href="/wiki/Vincenzo_Gamba" title="Vincenzo Gamba">son</a>, who drew a sketch of it. The son began construction of a prototype, but both he and Galileo died before it was completed.</p><div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Anchor_escapement">Anchor escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=10" title="Edit section: Anchor escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Anchor_escapement" title="Anchor escapement">Anchor escapement</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Anchor_escapement_animation_217x328px.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/29/Anchor_escapement_animation_217x328px.gif/150px-Anchor_escapement_animation_217x328px.gif" decoding="async" width="150" height="227" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/2/29/Anchor_escapement_animation_217x328px.gif 1.5x" data-file-width="217" data-file-height="328" /></a><figcaption>Animation of anchor escapement</figcaption></figure> <p>Invented around 1657 by <a href="/wiki/Robert_Hooke" title="Robert Hooke">Robert Hooke</a>, the anchor (see animation) quickly superseded the verge to become the standard escapement used in <a href="/wiki/Pendulum_clock" title="Pendulum clock">pendulum clocks</a> through to the 19th century. Its advantage was that it reduced the wide pendulum swing angles of the verge to 3–6°, making the pendulum nearly <a href="/wiki/Isochronous" class="mw-redirect" title="Isochronous">isochronous</a>, and allowing the use of longer, slower-moving pendulums, which used less energy. The anchor is responsible for the long narrow shape of most pendulum clocks, and for the development of the <a href="/wiki/Grandfather_clock" title="Grandfather clock">grandfather clock</a>, the first anchor clock to be sold commercially, which was invented around 1680 by William Clement, who disputed credit for the escapement with Hooke. </p><p>The anchor consists of an escape wheel with pointed, backward slanted teeth, and an "anchor"-shaped piece pivoted above it which rocks from side to side, linked to the pendulum. The anchor has slanted pallets on the arms which alternately catch on the teeth of the escape wheel, receiving impulses. Operation is mechanically similar to the verge escapement, and it has two of the verge's disadvantages: (1) The pendulum is constantly being pushed by an escape wheel tooth throughout its cycle, and is never allowed to swing freely, which disturbs its isochronism, and (2) it is a <i>recoil</i> escapement; the anchor pushes the escape wheel backward during part of its cycle. This causes <a href="/wiki/Backlash_(engineering)" title="Backlash (engineering)">backlash</a>, increased wear in the clock's gears, and inaccuracy. These problems were eliminated in the <a href="/wiki/Deadbeat_escapement" class="mw-redirect" title="Deadbeat escapement">deadbeat escapement</a>, which slowly replaced the anchor in precision clocks. </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Deadbeat_escapement">Deadbeat escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=11" title="Edit section: Deadbeat escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Anchor_escapement#Deadbeat_escapement" title="Anchor escapement">Anchor escapement § Deadbeat escapement</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Graham_Escapement.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Graham_Escapement.svg/150px-Graham_Escapement.svg.png" decoding="async" width="150" height="197" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Graham_Escapement.svg/225px-Graham_Escapement.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Graham_Escapement.svg/300px-Graham_Escapement.svg.png 2x" data-file-width="475" data-file-height="625" /></a><figcaption>Deadbeat escapement<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> diagram showing escape wheel (a), pallets (b), and pendulum crutch (c)</figcaption></figure> <p>The Graham or deadbeat escapement was an improvement of the anchor escapement first made by <a href="/wiki/Thomas_Tompion" title="Thomas Tompion">Thomas Tompion</a> to a design by <a href="/wiki/Richard_Towneley" title="Richard Towneley">Richard Towneley</a> in 1675,<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> although it is often credited to Tompion's successor <a href="/wiki/George_Graham_(clockmaker)" title="George Graham (clockmaker)">George Graham</a> who popularized it in 1715.<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> In the anchor escapement the swing of the pendulum pushes the escape wheel backward during part of its cycle. This "recoil" disturbs the motion of the pendulum, causing inaccuracy, and reverses the direction of the gear train, causing <a href="/wiki/Backlash_(engineering)" title="Backlash (engineering)">backlash</a> and introducing high loads into the system, leading to friction and wear. The main advantage of the deadbeat is that it eliminated recoil.<sup id="cite_ref-Headrick_14-3" class="reference"><a href="#cite_note-Headrick-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p><p>In the deadbeat, the pallets have a second curved "locking" face on them, concentric about the pivot on which the anchor turns. During the extremities of the pendulum's swing, the escape wheel tooth rests against this locking face, providing no impulse to the pendulum, which prevents recoil. Near the bottom of the pendulum's swing, the tooth slides off the locking face onto the angled "impulse" face, giving the pendulum a push, before the pallet releases the tooth. The deadbeat was first used in precision regulator clocks, but because of its greater accuracy it superseded the anchor in the 19th century. It is used in almost all modern pendulum clocks,<sup id="cite_ref-Rawlings_31-1" class="reference"><a href="#cite_note-Rawlings-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> except for tower clocks, which often use gravity escapements. </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Pin_wheel_escapement">Pin wheel escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=12" title="Edit section: Pin wheel escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Pin-pallet_escapement" title="Pin-pallet escapement">Pin-pallet escapement</a>.</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:PinWheelEscapement.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b3/PinWheelEscapement.JPG/220px-PinWheelEscapement.JPG" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b3/PinWheelEscapement.JPG/330px-PinWheelEscapement.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b3/PinWheelEscapement.JPG/440px-PinWheelEscapement.JPG 2x" data-file-width="2560" data-file-height="1920" /></a><figcaption>Pin wheel escapement of <a href="/wiki/South_Mimms" title="South Mimms">South Mymms</a> tower clock</figcaption></figure> <p>Invented around 1741 by Louis Amant, this version of a deadbeat escapement can be made quite rugged. Instead of using teeth, the escape wheel has round pins that are stopped and released by a scissors-like anchor. This escapement, which is also called the Amant escapement or (in Germany) the <a href="/wiki/Johann_Mannhardt" title="Johann Mannhardt">Mannhardt</a> escapement, is used quite often in tower clocks.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (January 2014)">citation needed</span></a></i>]</sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Detent_escapement">Detent escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=13" title="Edit section: Detent escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1273380762/mw-parser-output/.tmulti"><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:472px;max-width:472px"><div class="trow"><div class="tsingle" style="width:196px;max-width:196px"><div class="thumbimage" style="height:158px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Le_Roy_escapement_mechanism.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Le_Roy_escapement_mechanism.jpg/194px-Le_Roy_escapement_mechanism.jpg" decoding="async" width="194" height="159" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Le_Roy_escapement_mechanism.jpg/291px-Le_Roy_escapement_mechanism.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Le_Roy_escapement_mechanism.jpg/388px-Le_Roy_escapement_mechanism.jpg 2x" data-file-width="646" data-file-height="528" /></a></span></div><div class="thumbcaption">First detent escapement by <a href="/wiki/Pierre_Le_Roy" title="Pierre Le Roy">Pierre Le Roy</a> 1748</div></div><div class="tsingle" style="width:272px;max-width:272px"><div class="thumbimage" style="height:158px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Diagram_of_the_chronometer_detent_escapement_Britten%27s_Clock_and_Watchmaker%27s_Handbook_9th_Edition_1896.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/68/Diagram_of_the_chronometer_detent_escapement_Britten%27s_Clock_and_Watchmaker%27s_Handbook_9th_Edition_1896.jpg/270px-Diagram_of_the_chronometer_detent_escapement_Britten%27s_Clock_and_Watchmaker%27s_Handbook_9th_Edition_1896.jpg" decoding="async" width="270" height="158" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/68/Diagram_of_the_chronometer_detent_escapement_Britten%27s_Clock_and_Watchmaker%27s_Handbook_9th_Edition_1896.jpg/405px-Diagram_of_the_chronometer_detent_escapement_Britten%27s_Clock_and_Watchmaker%27s_Handbook_9th_Edition_1896.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/68/Diagram_of_the_chronometer_detent_escapement_Britten%27s_Clock_and_Watchmaker%27s_Handbook_9th_Edition_1896.jpg/540px-Diagram_of_the_chronometer_detent_escapement_Britten%27s_Clock_and_Watchmaker%27s_Handbook_9th_Edition_1896.jpg 2x" data-file-width="800" data-file-height="468" /></a></span></div><div class="thumbcaption">Earnshaw's detent escapement, used widely in chronometers</div></div></div></div></div> <p>The <a href="/wiki/Detent" title="Detent">detent</a> or chronometer escapement was used in <a href="/wiki/Marine_chronometer" title="Marine chronometer">marine chronometers</a>, although some precision watches during the 18th and 19th centuries also used it.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> It was considered the most accurate of the balance wheel escapements before the beginning of the 20th century, when lever escapement chronometers began to outperform them in competition.<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> The early form was invented by <a href="/wiki/Pierre_Le_Roy" title="Pierre Le Roy">Pierre Le Roy</a> in 1748, who created a pivoted detent type of escapement, though this was theoretically deficient.<sup id="cite_ref-Betts_44-0" class="reference"><a href="#cite_note-Betts-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Macey_45-0" class="reference"><a href="#cite_note-Macey-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> The first effective design of detent escapement was invented by <a href="/wiki/John_Arnold_(watchmaker)" title="John Arnold (watchmaker)">John Arnold</a> around 1775, but with the detent pivoted. This escapement was modified by <a href="/wiki/Thomas_Earnshaw" title="Thomas Earnshaw">Thomas Earnshaw</a> in 1780 and patented by Wright (for whom he worked) in 1783; however, as depicted in the patent it was unworkable. Arnold also designed a spring detent escapement but, with improved design, Earnshaw's version eventually prevailed as the basic idea underwent several minor modifications during the last decade of the 18th century. The final form appeared around 1800, and this design was used until mechanical chronometers became obsolete in the 1970s. </p><p>The detent is a detached escapement; it allows the balance wheel to swing undisturbed during most of its cycle, except the brief impulse period, which is only given once per cycle (every other swing).<sup id="cite_ref-Betts_44-1" class="reference"><a href="#cite_note-Betts-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> Because the driving escape wheel tooth moves almost parallel to the pallet, the escapement has little friction and does not need oiling. For these reasons among others, the detent was considered the most accurate escapement for balance wheel timepieces.<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> John Arnold was the first to use the detent escapement with an overcoil <a href="/wiki/Balance_spring" title="Balance spring">balance spring</a> (patented 1782), and with this improvement his watches were the first truly accurate pocket timekeepers, keeping time to within 1 or 2 seconds per day. These were produced from 1783 onwards. </p><p>However, the escapement had disadvantages that limited its use in watches: it was fragile and required skilled maintenance; it was not self-starting, so if the watch was jarred in use so the balance wheel stopped, it would not start up again; and it was harder to manufacture in volume. Therefore, the self-starting <a href="/wiki/Lever_escapement" title="Lever escapement">lever escapement</a> became dominant in watches. </p> <div class="mw-heading mw-heading3"><h3 id="Cylinder_escapement">Cylinder escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=14" title="Edit section: Cylinder escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1273380762/mw-parser-output/.tmulti"><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:412px;max-width:412px"><div class="trow"><div class="tsingle" style="width:195px;max-width:195px"><div class="thumbimage" style="height:158px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Tidens_naturl%C3%A6re_fig27.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Tidens_naturl%C3%A6re_fig27.png/193px-Tidens_naturl%C3%A6re_fig27.png" decoding="async" width="193" height="159" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Tidens_naturl%C3%A6re_fig27.png/290px-Tidens_naturl%C3%A6re_fig27.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Tidens_naturl%C3%A6re_fig27.png/386px-Tidens_naturl%C3%A6re_fig27.png 2x" data-file-width="1068" data-file-height="880" /></a></span></div><div class="thumbcaption">Cylinder escapement. The balance wheel is attached to the cylinder (B).</div></div><div class="tsingle" style="width:213px;max-width:213px"><div class="thumbimage" style="height:158px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Cylinder_Detail_Animation.gif" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/54/Cylinder_Detail_Animation.gif/211px-Cylinder_Detail_Animation.gif" decoding="async" width="211" height="158" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/5/54/Cylinder_Detail_Animation.gif 1.5x" data-file-width="300" data-file-height="225" /></a></span></div><div class="thumbcaption">Animation of cylinder escapement showing how the cylinder part works</div></div></div></div></div> <p>The horizontal or cylinder escapement, invented by <a href="/wiki/Thomas_Tompion" title="Thomas Tompion">Thomas Tompion</a> in 1695<sup id="cite_ref-Britten_48-0" class="reference"><a href="#cite_note-Britten-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> and perfected by <a href="/wiki/George_Graham_(clockmaker)" title="George Graham (clockmaker)">George Graham</a> in 1726,<sup id="cite_ref-Du1_49-0" class="reference"><a href="#cite_note-Du1-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> was one of the escapements which replaced the verge escapement in pocketwatches after 1700. A major attraction was that it was much thinner than the verge, allowing watches to be made fashionably slim. Clockmakers found it suffered from excessive wear, so it was not much used during the 18th century, except in a few high-end watches with cylinders made from <a href="/wiki/Ruby" title="Ruby">ruby</a>. The French solved this problem by making the cylinder and escape wheel of hardened steel,<sup id="cite_ref-Britten_48-1" class="reference"><a href="#cite_note-Britten-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> and the escapement was used in large numbers in inexpensive French and Swiss pocketwatches and small clocks from the mid-19th to the 20th century. </p><p>Rather than pallets, the escapement uses a cutaway cylinder on the balance wheel shaft, which the escape teeth enter one by one.<sup id="cite_ref-Britten_48-2" class="reference"><a href="#cite_note-Britten-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Du1_49-1" class="reference"><a href="#cite_note-Du1-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> Each wedge-shaped tooth impulses the balance wheel by pressure on the cylinder edge as it enters, is held inside the cylinder as it turns, and impulses the wheel again as it leaves out the other side. The wheel usually had 15 teeth and impulsed the balance over an angle of 20° to 40° in each direction.<sup id="cite_ref-Britten_48-3" class="reference"><a href="#cite_note-Britten-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> It is a frictional rest escapement, with the teeth in contact with the cylinder over the whole balance wheel cycle, and so was not as accurate as "detached" escapements like the lever, and the high friction forces caused excessive wear and necessitated more frequent cleaning.<sup id="cite_ref-Du1_49-2" class="reference"><a href="#cite_note-Du1-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Duplex_escapement">Duplex escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=15" title="Edit section: Duplex escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Duplex_Escapement.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/19/Duplex_Escapement.png/220px-Duplex_Escapement.png" decoding="async" width="220" height="250" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/19/Duplex_Escapement.png/330px-Duplex_Escapement.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/19/Duplex_Escapement.png/440px-Duplex_Escapement.png 2x" data-file-width="640" data-file-height="726" /></a><figcaption>Duplex escapement, showing (A) escape wheel, (B) locking tooth, (C) impulse tooth, (D) pallet, (E) ruby disk. The pallet and disk are attached to the balance wheel arbor, but the wheel is not shown.</figcaption></figure> <p>The duplex watch escapement was invented by <a href="/wiki/Robert_Hooke" title="Robert Hooke">Robert Hooke</a> around 1700, improved by Jean Baptiste Dutertre and <a href="/wiki/Pierre_Le_Roy" title="Pierre Le Roy">Pierre Le Roy</a>, and put in final form by Thomas Tyrer, who patented it in 1782.<sup id="cite_ref-Nelthropp_1873_50-0" class="reference"><a href="#cite_note-Nelthropp_1873-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> The early forms had two escape wheels. The duplex escapement was difficult to make but achieved much higher accuracy than the cylinder escapement—it could equal that of the (early) <a href="/wiki/Lever_escapement" title="Lever escapement">lever escapement</a>, and when carefully made was almost as good as a detent escapement. <sup id="cite_ref-Nelthropp_1873_50-1" class="reference"><a href="#cite_note-Nelthropp_1873-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> <sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> <sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> It was used in quality English pocketwatches from about 1790 to 1860, <sup id="cite_ref-Glasgow1885_53-0" class="reference"><a href="#cite_note-Glasgow1885-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> <sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup> and in the Waterbury, a cheap American "everyman's watch", during 1880–1898.<sup id="cite_ref-56" class="reference"><a href="#cite_note-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> <sup id="cite_ref-57" class="reference"><a href="#cite_note-57"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup> </p><p>In the duplex, as in the <a href="#Detent_escapement">chronometer escapement</a> to which it has similarities, the balance wheel only receives an impulse during one of the two swings in its cycle. <sup id="cite_ref-Glasgow1885_53-1" class="reference"><a href="#cite_note-Glasgow1885-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup> The escape wheel has two sets of teeth (hence the name "duplex"); long locking teeth project from the side of the wheel, and short impulse teeth stick up axially from the top. The cycle starts with a locking tooth resting against the ruby disk. As the balance wheel swings counterclockwise through its center position, the notch in the ruby disk releases the tooth. As the escape wheel turns, the pallet is in just the right position to receive a push from an impulse tooth. Then the next locking tooth drops onto the ruby roller and stays there while the balance wheel completes its cycle and swings back clockwise, and the process repeats. During the clockwise swing, the impulse tooth falls momentarily into the ruby roller notch again but is not released. </p><p>The duplex is technically a <i>frictional rest</i> escapement; the tooth resting against the roller adds some friction to the balance wheel during its swing<sup id="cite_ref-Glasgow1885_53-2" class="reference"><a href="#cite_note-Glasgow1885-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-58" class="reference"><a href="#cite_note-58"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup> but this is very minimal. As in the chronometer, there is little sliding friction during impulse since pallet and impulse tooth are moving almost parallel, so little lubrication is needed. <sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup> However, it lost favor to the lever escapement; its tight tolerances and sensitivity to shock made duplex watches unsuitable for active people. Like the chronometer, it is not self-starting and is vulnerable to "setting"—if a sudden jar stops the balance during its clockwise swing, it cannot restart. </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Lever_escapement">Lever escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=16" title="Edit section: Lever escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Lever_escapement" title="Lever escapement">Lever escapement</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1273380762/mw-parser-output/.tmulti"><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:412px;max-width:412px"><div class="trow"><div class="tsingle" style="width:231px;max-width:231px"><div class="thumbimage" style="height:248px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Anker_01.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/49/Anker_01.svg/229px-Anker_01.svg.png" decoding="async" width="229" height="248" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/49/Anker_01.svg/344px-Anker_01.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/49/Anker_01.svg/458px-Anker_01.svg.png 2x" data-file-width="792" data-file-height="859" /></a></span></div><div class="thumbcaption">Inline or Swiss lever escapement</div></div><div class="tsingle" style="width:177px;max-width:177px"><div class="thumbimage" style="height:248px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Paletteankerhemmung.gif" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/75/Paletteankerhemmung.gif/175px-Paletteankerhemmung.gif" decoding="async" width="175" height="248" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/7/75/Paletteankerhemmung.gif 1.5x" data-file-width="260" data-file-height="368" /></a></span></div><div class="thumbcaption">Animation of lever escapement showing movement of lever only</div></div></div></div></div> <p>The <a href="/wiki/Lever_escapement" title="Lever escapement">lever escapement</a>, invented by <a href="/wiki/Thomas_Mudge_(horologist)" title="Thomas Mudge (horologist)">Thomas Mudge</a> in 1750, has been used in the vast majority of watches since the 19th century. Its advantages are (1) it is a "detached" escapement, in which (unlike the cylinder or duplex escapements) the balance wheel is only in contact with the lever during the short impulse period when it swings through its centre position and swings freely the rest of its cycle, increasing accuracy; and (2) it is a self-starting escapement, so if the balance wheel stops because the watch is shaken, it will automatically start again. The original form was the rack lever escapement, in which the lever and the balance wheel were always in contact via a gear rack on the lever. Later, it was realized that all the teeth from the gears could be removed except one, and this created the detached lever escapement. British watchmakers used the English detached lever, in which the lever was at right angles to the balance wheel. Later Swiss and American manufacturers used the inline lever, in which the lever is inline between the balance wheel and the escape wheel; this is the form used in modern watches. In 1798, Louis Perron invented an inexpensive, less accurate form called the <a href="/wiki/Pin-pallet_escapement" title="Pin-pallet escapement">pin-pallet escapement</a>, which was used in cheap "<a href="/wiki/Dollar_watch" title="Dollar watch">dollar watches</a>" in the early 20th century and is still used in cheap <a href="/wiki/Alarm_clock" title="Alarm clock">alarm clocks</a> and kitchen timers.<sup id="cite_ref-60" class="reference"><a href="#cite_note-60"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Grasshopper_escapement">Grasshopper escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=17" title="Edit section: Grasshopper escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Grasshopper_escapement" title="Grasshopper escapement">Grasshopper escapement</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1273380762/mw-parser-output/.tmulti"><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:312px;max-width:312px"><div class="trow"><div class="tsingle" style="width:153px;max-width:153px"><div class="thumbimage" style="height:211px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Grasshopper_escapement.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Grasshopper_escapement.png/151px-Grasshopper_escapement.png" decoding="async" width="151" height="211" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/0/0e/Grasshopper_escapement.png 1.5x" data-file-width="219" data-file-height="306" /></a></span></div><div class="thumbcaption">Grasshopper escapement diagram (1820)</div></div><div class="tsingle" style="width:155px;max-width:155px"><div class="thumbimage" style="height:211px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Grasshopper-escapement_colored.gif" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Grasshopper-escapement_colored.gif/153px-Grasshopper-escapement_colored.gif" decoding="async" width="153" height="212" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Grasshopper-escapement_colored.gif/230px-Grasshopper-escapement_colored.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Grasshopper-escapement_colored.gif/306px-Grasshopper-escapement_colored.gif 2x" data-file-width="420" data-file-height="583" /></a></span></div><div class="thumbcaption">Animation of one form of grasshopper escapement</div></div></div></div></div> <p>A rare but interesting mechanical escapement is <a href="/wiki/John_Harrison" title="John Harrison">John Harrison</a>'s <a href="/wiki/Grasshopper_escapement" title="Grasshopper escapement">grasshopper escapement</a> invented in 1722. In this escapement, the pendulum is driven by two hinged arms (pallets). As the pendulum swings, the end of one arm catches on the escape wheel and drives it slightly backwards; this releases the other arm which moves out of the way to allow the escape wheel to pass. When the pendulum swings back again, the other arm catches the wheel, pushes it back and releases the first arm, and so on. The grasshopper escapement has been used in very few clocks since Harrison's time. Grasshopper escapements made by Harrison in the 18th century are still operating. Most escapements wear far more quickly, and waste far more energy. However, like other early escapements, the grasshopper impulses the pendulum throughout its cycle; it is never allowed to swing freely, causing error due to variations in drive force,<sup id="cite_ref-Du2_61-0" class="reference"><a href="#cite_note-Du2-61"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> and 19th-century clockmakers found it uncompetitive with more detached escapements like the deadbeat.<sup id="cite_ref-Britten2_62-0" class="reference"><a href="#cite_note-Britten2-62"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Du2_61-1" class="reference"><a href="#cite_note-Du2-61"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> Nevertheless, with enough care in construction it is capable of accuracy. A modern experimental grasshopper clock, the Burgess Clock B, had a measured error of only <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac"><span class="num">5</span>⁄<span class="den">8</span></span> of a second during 100 running days.<sup id="cite_ref-63" class="reference"><a href="#cite_note-63"><span class="cite-bracket">[</span>63<span class="cite-bracket">]</span></a></sup> After two years of operation, it had an error of only ±0.5 sec, after barometric correction.<sup id="cite_ref-64" class="reference"><a href="#cite_note-64"><span class="cite-bracket">[</span>64<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-65" class="reference"><a href="#cite_note-65"><span class="cite-bracket">[</span>65<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Gravity_escapement">Gravity escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=18" title="Edit section: Gravity escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Gravity_escapement_2.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/1/10/Gravity_escapement_2.gif" decoding="async" width="220" height="396" class="mw-file-element" data-file-width="220" data-file-height="396" /></a><figcaption>Double three-legged gravity escapement</figcaption></figure><p>A gravity escapement uses a small weight or a weak spring to give an impulse directly to the pendulum. The earliest form consisted of two arms which were pivoted very close to the suspension spring of the pendulum with one arm on each side of the pendulum. Each arm carried a small deadbeat pallet with an angled plane leading to it. When the pendulum lifted one arm far enough, its pallet would release the escape wheel. Almost immediately, another tooth on the escape wheel would start to slide up the angle face on the other arm thereby lifting the arm. It would reach the pallet and stop. The other arm meanwhile was still in contact with the pendulum and coming down again to a point lower than it had started from. This lowering of the arm provides the impulse to the pendulum. </p><p>The design was developed steadily from the middle of the 18th century to the middle of the 19th century. It eventually became the escapement of choice for <a href="/wiki/Turret_clock" title="Turret clock">turret clocks</a>, because their wheel trains are subjected to large variations in drive force caused by the large exterior hands, with their varying wind, snow, and ice loads. Since in a gravity escapement, the drive force from the wheel train does not itself impel the pendulum but merely resets the weights that provide the impulse, the escapement is not affected by variations in drive force. </p><p>The "double three-legged gravity escapement" shown here is a form of escapement first devised by a barrister named Bloxam and later improved by <a href="/wiki/Edmund_Beckett,_1st_Baron_Grimthorpe" title="Edmund Beckett, 1st Baron Grimthorpe">Lord Grimthorpe</a>. It is the standard for all accurate tower clocks. In the animation, the two "gravity arms" are coloured blue and red. The two three-legged escape wheels are also coloured blue and red. They work in two parallel planes so that the blue wheel only impacts the locking block on the blue arm and the red wheel only impacts the red arm. In a real escapement, these impacts give rise to loud audible "ticks" (indicated in the animation by the appearance of an asterisk (*) beside the locking blocks). The three black lifting pins are key to the operation of the escapement. They cause the weighted gravity arms to be raised by an amount indicated by the pair of parallel lines on each side of the escapement. This gain in potential energy is the energy given to the pendulum on each cycle. For the <a href="/wiki/Trinity_College_Clock" title="Trinity College Clock">Trinity College Cambridge Clock</a>, a mass of around 50 grams is lifted through 3 mm each 1.5 seconds, which works out to 1 mW of power. The driving power from the falling weight is about 12 mW, so there is a substantial excess of power used to drive the escapement. Much of this energy is dissipated in the acceleration and deceleration of the frictional "fly" attached to the escape wheels. The great clock in Elizabeth Tower at Westminster that rings London's <a href="/wiki/Big_Ben" title="Big Ben">Big Ben</a> uses a double three-legged gravity escapement. </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading3"><h3 id="Coaxial_escapement">Coaxial escapement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=19" title="Edit section: Coaxial escapement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Coaxial_escapement" title="Coaxial escapement">Coaxial escapement</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1273380762/mw-parser-output/.tmulti"><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:412px;max-width:412px"><div class="trow"><div class="tsingle" style="width:200px;max-width:200px"><div class="thumbimage" style="height:197px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Coaxial_Toon_600.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Coaxial_Toon_600.svg/198px-Coaxial_Toon_600.svg.png" decoding="async" width="198" height="198" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Coaxial_Toon_600.svg/297px-Coaxial_Toon_600.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Coaxial_Toon_600.svg/396px-Coaxial_Toon_600.svg.png 2x" data-file-width="420" data-file-height="420" /></a></span></div><div class="thumbcaption">Coaxial escapement</div></div><div class="tsingle" style="width:208px;max-width:208px"><div class="thumbimage" style="height:197px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:CoaxialEscapement.gif" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f5/CoaxialEscapement.gif/206px-CoaxialEscapement.gif" decoding="async" width="206" height="198" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f5/CoaxialEscapement.gif/309px-CoaxialEscapement.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/f/f5/CoaxialEscapement.gif 2x" data-file-width="400" data-file-height="384" /></a></span></div><div class="thumbcaption">Animation of coaxial escapement</div></div></div></div></div> <p>Invented around 1974<sup id="cite_ref-66" class="reference"><a href="#cite_note-66"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup> and patented in 1980<sup id="cite_ref-67" class="reference"><a href="#cite_note-67"><span class="cite-bracket">[</span>67<span class="cite-bracket">]</span></a></sup> by British watchmaker <a href="/wiki/George_Daniels_(watchmaker)" title="George Daniels (watchmaker)">George Daniels</a>, the coaxial escapement is one of the few new watch escapements adopted commercially in modern times. </p><p>It could be regarded<sup class="noprint Inline-Template" style="margin-left:0.1em; white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Words_to_watch#Unsupported_attributions" title="Wikipedia:Manual of Style/Words to watch"><span title="The material near this tag may use weasel words or too-vague attribution. (October 2019)">according to whom?</span></a></i>]</sup> as having its distant origins in the escapement invented by Robert Robin circa 1792, which gives a single impulse in one direction. Yet with the locking achieved by passive lever pallets,<sup id="cite_ref-68" class="reference"><a href="#cite_note-68"><span class="cite-bracket">[</span>68<span class="cite-bracket">]</span></a></sup> the design of the coaxial escapement is more akin to the Fasoldt escapement (another Robin variant), which was invented and patented by the American Charles Fasoldt in 1859.<sup id="cite_ref-69" class="reference"><a href="#cite_note-69"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-70" class="reference"><a href="#cite_note-70"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-71" class="reference"><a href="#cite_note-71"><span class="cite-bracket">[</span>71<span class="cite-bracket">]</span></a></sup> Both Robin and Fasoldt escapements give impulse in one direction only. </p><p>The Fasoldt escapement has a lever with unequal drops; this engages with two escape wheels of differing diameters. The smaller impulse wheel acts on the single pallet at the end of the lever, whilst the pointed lever pallets lock on the larger wheel. The balance engages with and is impelled by the lever through a roller pin and lever fork. The lever "anchor" pallet locks the larger wheel; when this is unlocked, a pallet on the end of the lever is given an impulse by the smaller wheel through the lever fork. The return stroke is "dead", with the anchor pallets serving only to lock and unlock, impulse being given in one direction through the single lever pallet. As with the duplex, the locking wheel is larger in order to reduce pressure and thus friction. </p><p>Daniels' coaxial escapement, however, achieves a double impulse with passive lever pallets serving only to lock and unlock the larger wheel. On one side, impulse is given by means of the smaller wheel acting on the lever pallet through the roller and impulse pin. On the return, the lever again unlocks the larger wheel, which gives an impulse directly onto an impulse roller on the balance staff. </p><p>The main advantage is that this enables both impulses to occur on or around the centre line, with disengaging friction in both directions.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (August 2022)">citation needed</span></a></i>]</sup> This mode of impulse is in theory superior to the lever escapement, which has engaging friction on the entry pallet. For long, this was recognized as a disturbing influence on the isochronism of the balance.<sup id="cite_ref-72" class="reference"><a href="#cite_note-72"><span class="cite-bracket">[</span>72<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Maddox_73-0" class="reference"><a href="#cite_note-Maddox-73"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup> </p><p>Purchasers no longer buy mechanical watches primarily for their accuracy, so manufacturers had little interest in investing in the tooling required to manufacture coaxial escapements; although finally, Omega adopted it in 1990.<sup id="cite_ref-Maddox_73-1" class="reference"><a href="#cite_note-Maddox-73"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Other_modern_watch_escapements">Other modern watch escapements</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=20" title="Edit section: Other modern watch escapements"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:The_Constant_Escapement.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/The_Constant_Escapement.png/220px-The_Constant_Escapement.png" decoding="async" width="220" height="109" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/The_Constant_Escapement.png/330px-The_Constant_Escapement.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/37/The_Constant_Escapement.png/440px-The_Constant_Escapement.png 2x" data-file-width="1157" data-file-height="575" /></a><figcaption>Illustration of the constant escapement by Girard-Perregaux</figcaption></figure> <p>Since low-cost <a href="/wiki/Quartz_watch" class="mw-redirect" title="Quartz watch">quartz watches</a> can achieve far greater accuracy than any mechanical watch, improved escapement designs are no longer motivated by practical timekeeping needs but as novelties in the high-end watch market. In an effort to attract publicity, in recent decades some high-end mechanical watchmakers have introduced new escapements. None of these have been adopted by any watchmakers beyond their original creator. </p><p>Based on patents initially submitted by <a href="/wiki/Rolex" title="Rolex">Rolex</a> on behalf of inventor Nicolas Déhon,<sup id="cite_ref-74" class="reference"><a href="#cite_note-74"><span class="cite-bracket">[</span>74<span class="cite-bracket">]</span></a></sup> the constant escapement was developed by <a href="/wiki/Girard-Perregaux" title="Girard-Perregaux">Girard-Perregaux</a> as working prototypes in 2008 (Déhon was then head of Girard-Perregaux R&D department) and in watches by 2013. </p><p>The key component of this escapement is a silicon buckled-blade which stores elastic energy. This blade is flexed to a point close to its unstable state and released with a snap each swing of the balance wheel to give the wheel an impulse, after which it is cocked again by the wheel train. The advantage claimed is that since the blade imparts the same amount of energy to the wheel each release, the balance wheel is isolated from variations in impulse force due to the wheel train and mainspring which cause inaccuracies in conventional escapements. </p><p><a href="/wiki/Parmigiani_Fleurier" title="Parmigiani Fleurier">Parmigiani Fleurier</a> with its Genequand escapement and <a href="/wiki/Ulysse_Nardin" title="Ulysse Nardin">Ulysse Nardin</a> with its Ulysse Anchor escapement have taken advantage of the properties of silicon flat springs. The independent watchmaker, De Bethune, has developed a concept where a magnet makes a resonator vibrate at high frequency, replacing the traditional <a href="/wiki/Balance_spring" title="Balance spring">balance spring</a>.<sup id="cite_ref-75" class="reference"><a href="#cite_note-75"><span class="cite-bracket">[</span>75<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Electromechanical_escapements">Electromechanical escapements</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=21" title="Edit section: Electromechanical escapements"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the late 19th century, electromechanical escapements were developed for pendulum clocks. In these, a switch or <a href="/wiki/Phototube" title="Phototube">phototube</a> energised an <a href="/wiki/Electromagnet" title="Electromagnet">electromagnet</a> for a brief section of the pendulum's swing. On some clocks, the pulse of electricity that drove the pendulum also drove a plunger to move the gear train. </p> <div class="mw-heading mw-heading3"><h3 id="Hipp_clock">Hipp clock</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=22" title="Edit section: Hipp clock"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 1843, <a href="/wiki/Matth%C3%A4us_Hipp" title="Matthäus Hipp">Matthäus Hipp</a> first mentioned a purely mechanical clock being driven by a switch called "echappement à palette".<sup id="cite_ref-76" class="reference"><a href="#cite_note-76"><span class="cite-bracket">[</span>76<span class="cite-bracket">]</span></a></sup> A varied version of that escapement has been used from the 1860s inside electrically driven pendulum clocks, the so-called "hipp-toggle".<sup id="cite_ref-77" class="reference"><a href="#cite_note-77"><span class="cite-bracket">[</span>77<span class="cite-bracket">]</span></a></sup> Since the 1870s, in an improved version the pendulum drove a ratchet wheel via a <a href="/wiki/Pawl" title="Pawl">pawl</a> on the pendulum rod, and the ratchet wheel drove the rest of the clock train to indicate the time. The pendulum was not impelled on every swing or even at a set interval of time—it was only impelled when its arc of swing had decayed below a certain level. As well as the counting pawl, the pendulum carried a small vane, known as a Hipp's toggle, pivoted at the top, which was completely free to swing. It was placed so that it dragged across a triangular polished block with a vee-groove in the top of it. When the arc of swing of the pendulum was large enough, the vane crossed the groove and swung free on the other side. If the arc was too small the vane never left the far side of the groove, and when the pendulum swung back it pushed the block strongly downwards. The block carried a contact which completed the circuit to the electromagnet which impelled the pendulum. The pendulum was only impelled as required. </p><p>This type of clock was widely used as a <a href="/wiki/Master_clock" title="Master clock">master clock</a> in large buildings to control numerous slave clocks. Most telephone exchanges used such a clock to control timed events such as were needed to control the setup and charging of telephone calls by issuing pulses of varying durations periodically, such as every second. </p> <div class="mw-heading mw-heading3"><h3 id="Synchronome_switch">Synchronome switch</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=23" title="Edit section: Synchronome switch"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Designed in 1895 by <a href="/wiki/Frank_Hope-Jones" title="Frank Hope-Jones">Frank Hope-Jones</a>, the Synchronome switch and gravity escapement were the basis for the majority of the Synchronome Company's clocks in the 20th century,<sup id="cite_ref-78" class="reference"><a href="#cite_note-78"><span class="cite-bracket">[</span>78<span class="cite-bracket">]</span></a></sup> as well as the basis of the slave pendulum in the <a href="/wiki/Shortt%E2%80%93Synchronome_clock" title="Shortt–Synchronome clock">Shortt-Synchronome free pendulum clock</a>.<sup id="cite_ref-79" class="reference"><a href="#cite_note-79"><span class="cite-bracket">[</span>79<span class="cite-bracket">]</span></a></sup> A gathering arm attached to the pendulum moves a 15-tooth count wheel in one position, with a pawl preventing movement in the reverse direction. The wheel has a vane attached which, once per 30-second turn, releases the gravity arm. When the gravity arm falls it pushes against a pallet attached directly to the pendulum. Once the arm has fallen, it makes an electrical contact that energises an electromagnet to reset the gravity arm and acts as the half-minute impulse for the slave clocks.<sup id="cite_ref-80" class="reference"><a href="#cite_note-80"><span class="cite-bracket">[</span>80<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Free_pendulum_clock">Free pendulum clock</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=24" title="Edit section: Free pendulum clock"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Shortt%E2%80%93Synchronome_clock" title="Shortt–Synchronome clock">Shortt–Synchronome clock</a></div> <p>In the 20th century, the English horologist <a href="/wiki/William_Hamilton_Shortt" title="William Hamilton Shortt">William Hamilton Shortt</a> invented a free pendulum clock, patented in September 1921 and manufactured by the Synchronome Company, with an accuracy of one-hundredth of a second a day. In this system, the timekeeping "master" pendulum—whose rod is made from a special steel-nickel alloy ( <a href="/wiki/Invar" title="Invar">Invar</a>) and whose length changes very little with temperature—swings as free of external influence as possible sealed in a vacuum chamber; it does virtually no <a href="/wiki/Work_(physics)" title="Work (physics)">work</a>. It is in mechanical contact with its escapement for only a fraction of a second every 30 seconds. A secondary "slave" pendulum turns a ratchet, which triggers an electromagnet slightly less than every 30 seconds. This electromagnet releases a gravity lever onto the escapement above the master pendulum. A fraction of a second later (but exactly every 30 seconds), the motion of the master pendulum releases the gravity lever to fall farther. In the process, the gravity lever gives a tiny impulse to the master pendulum, which keeps that pendulum swinging. The gravity lever falls onto a pair of contacts, completing a circuit that (1) energizes a second electromagnet to raise the gravity lever above the master pendulum to its top position, (2) sends a pulse to activate one or more clock dials, and (3) sends a pulse to a synchronizing mechanism that keeps the slave pendulum in step with the master pendulum. </p><p>Since it is the slave pendulum that releases the gravity lever, this synchronization is vital to the functioning of the clock. The synchronizing mechanism used a small spring attached to the shaft of the slave pendulum and an electromagnetic armature that would catch the spring if the slave pendulum was running slightly late, thus shortening the period of the slave pendulum for one swing. The slave pendulum was adjusted to run slightly slow, such that on approximately every other synchronization pulse the spring would be caught by the armature.<sup id="cite_ref-81" class="reference"><a href="#cite_note-81"><span class="cite-bracket">[</span>81<span class="cite-bracket">]</span></a></sup> </p><p>This form of clock became a standard for use in observatories (roughly 100 such clocks were manufactured<sup id="cite_ref-82" class="reference"><a href="#cite_note-82"><span class="cite-bracket">[</span>82<span class="cite-bracket">]</span></a></sup>) and was the first clock capable of detecting small variations in the speed of Earth's rotation. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=25" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Escapement_(radio_control)" class="mw-redirect" title="Escapement (radio control)">Escapement (radio control)</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Citations">Citations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=26" title="Edit section: Citations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 33em;"> <ol class="references"> <li id="cite_note-Marrison-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-Marrison_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Marrison_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFMarrison1948" class="citation journal cs1">Marrison, Warren (1948). <a rel="nofollow" class="external text" href="https://archive.org/details/bstj27-3-510">"The Evolution of the Quartz Crystal Clock"</a>. <i>Bell System Technical Journal</i>. <b>27</b> (3): <span class="nowrap">510–</span>588. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fj.1538-7305.1948.tb01343.x">10.1002/j.1538-7305.1948.tb01343.x</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070513175811/https://ieee-uffc.org/about-us/history/uffc-s-history/the-evolution-of-the-quartz-crystal-clock/">Archived</a> from the original on 2007-05-13<span class="reference-accessdate">. Retrieved <span class="nowrap">2007-06-06</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Bell+System+Technical+Journal&rft.atitle=The+Evolution+of+the+Quartz+Crystal+Clock&rft.volume=27&rft.issue=3&rft.pages=%3Cspan+class%3D%22nowrap%22%3E510-%3C%2Fspan%3E588&rft.date=1948&rft_id=info%3Adoi%2F10.1002%2Fj.1538-7305.1948.tb01343.x&rft.aulast=Marrison&rft.aufirst=Warren&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fbstj27-3-510&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><a href="#CITEREFWhite1964">White 1964</a>, p. 187</span> </li> <li id="cite_note-Cipolla-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Cipolla_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Cipolla_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCipolla2004" class="citation book cs1">Cipolla, Carlo M. (2004). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=YSf9MVxa2JEC&q=verge+escapement+technology&pg=PA31"><i>Clocks and Culture, 1300 to 1700</i></a>. W.W. Norton & Co. p. 31. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-393-32443-5" title="Special:BookSources/0-393-32443-5"><bdi>0-393-32443-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Clocks+and+Culture%2C+1300+to+1700&rft.pages=31&rft.pub=W.W.+Norton+%26+Co.&rft.date=2004&rft.isbn=0-393-32443-5&rft.aulast=Cipolla&rft.aufirst=Carlo+M.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DYSf9MVxa2JEC%26q%3Dverge%2Bescapement%2Btechnology%26pg%3DPA31&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Jesperson-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-Jesperson_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJespersenFitz-Randolph,_JaneRobb,_John1999" class="citation book cs1">Jespersen, James; Fitz-Randolph, Jane; Robb, John (1999). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Z7chuo4ebUAC&q=clock+resonance+pendulum&pg=PA42"><i>From Sundials to Atomic Clocks: Understanding Time and Frequency</i></a>. New York: Courier Dover. p. 39. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-486-40913-9" title="Special:BookSources/978-0-486-40913-9"><bdi>978-0-486-40913-9</bdi></a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230703114213/https://books.google.com/books?id=Z7chuo4ebUAC&q=clock+resonance+pendulum&pg=PA42">Archived</a> from the original on July 3, 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">October 30,</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=From+Sundials+to+Atomic+Clocks%3A+Understanding+Time+and+Frequency&rft.place=New+York&rft.pages=39&rft.pub=Courier+Dover&rft.date=1999&rft.isbn=978-0-486-40913-9&rft.aulast=Jespersen&rft.aufirst=James&rft.au=Fitz-Randolph%2C+Jane&rft.au=Robb%2C+John&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DZ7chuo4ebUAC%26q%3Dclock%2Bresonance%2Bpendulum%26pg%3DPA42&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Bloomfield-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-Bloomfield_5-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBloomfield2007" class="citation book cs1">Bloomfield, Louis (2007). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=_ZNxDwAAQBAJ"><i>How Everything Works: Making Physics Out of the Ordinary</i></a>. Wiley. p. 296. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-470-17066-3" title="Special:BookSources/978-0-470-17066-3"><bdi>978-0-470-17066-3</bdi></a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230404215125/https://books.google.com/books?id=_ZNxDwAAQBAJ">Archived</a> from the original on April 4, 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">March 19,</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=How+Everything+Works%3A+Making+Physics+Out+of+the+Ordinary&rft.pages=296&rft.pub=Wiley&rft.date=2007&rft.isbn=978-0-470-17066-3&rft.aulast=Bloomfield&rft.aufirst=Louis&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D_ZNxDwAAQBAJ&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-NIST1-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-NIST1_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20080511051339/http://tf.nist.gov/general/enc-ch.htm">"Clock"</a>. <i>Glossary, Time and Frequency Division</i>. US National Inst. of Science and Technology. Archived from <a rel="nofollow" class="external text" href="http://tf.nist.gov/general/enc-ch.htm">the original</a> on 11 May 2008<span class="reference-accessdate">. Retrieved <span class="nowrap">13 August</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Glossary%2C+Time+and+Frequency+Division&rft.atitle=Clock&rft_id=http%3A%2F%2Ftf.nist.gov%2Fgeneral%2Fenc-ch.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Lewis_2000_356f.-7"><span class="mw-cite-backlink">^ <a href="#cite_ref-Lewis_2000_356f._7-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Lewis_2000_356f._7-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLewis2020" class="citation book cs1">Lewis, Michael (2020). "Theoretical Hydraulics, Automata, and Water Clocks". In <a href="/wiki/%C3%96rjan_Wikander" title="Örjan Wikander">Wikander, Örjan</a> (ed.). <i>Handbook of Ancient Water Technology</i>. Technology and Change in History. Vol. 2. Leiden: Brill. pp. 343–369 (356f.). <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-90-04-11123-3" title="Special:BookSources/978-90-04-11123-3"><bdi>978-90-04-11123-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Theoretical+Hydraulics%2C+Automata%2C+and+Water+Clocks&rft.btitle=Handbook+of+Ancient+Water+Technology&rft.place=Leiden&rft.series=Technology+and+Change+in+History&rft.pages=343-369+%28356f.%29&rft.pub=Brill&rft.date=2020&rft.isbn=978-90-04-11123-3&rft.aulast=Lewis&rft.aufirst=Michael&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-needham_volume_4_part_2_165-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-needham_volume_4_part_2_165_8-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham1986">Needham 1986</a>, p. 165</span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham1986">Needham 1986</a>, p. 319</span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham1986">Needham 1986</a>, pp. 445, 448, 469–471</span> </li> <li id="cite_note-Derek-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-Derek_11-0">^</a></b></span> <span class="reference-text"><a href="/wiki/Derek_J._de_Solla_Price" title="Derek J. de Solla Price">Derek J. de Solla Price</a>, <a rel="nofollow" class="external text" href="http://www.gutenberg.org/files/30001/30001-h/30001-h.htm">On the Origin of Clockwork, Perpetual Motion Devices, and the Compass</a>, p.86</span> </li> <li id="cite_note-Hassan-12"><span class="mw-cite-backlink">^ <a href="#cite_ref-Hassan_12-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Hassan_12-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Ahmad Y. Hassan, <a rel="nofollow" class="external text" href="http://www.history-science-technology.com/Articles/articles%2071.htm">Transfer Of Islamic Technology To The West, Part II: Transmission Of Islamic Engineering</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080218171021/http://www.history-science-technology.com/Articles/articles%2071.htm">Archived</a> 2008-02-18 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, <i>History of Science and Technology in Islam</i>.</span> </li> <li id="cite_note-Ajram-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-Ajram_13-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAjram1992" class="citation book cs1">Ajram, K. (1992). "Appendix B". <i>Miracle of Islamic Science</i>. Knowledge House Publishers. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-911119-43-4" title="Special:BookSources/0-911119-43-4"><bdi>0-911119-43-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Appendix+B&rft.btitle=Miracle+of+Islamic+Science&rft.pub=Knowledge+House+Publishers&rft.date=1992&rft.isbn=0-911119-43-4&rft.aulast=Ajram&rft.aufirst=K.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Headrick-14"><span class="mw-cite-backlink">^ <a href="#cite_ref-Headrick_14-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Headrick_14-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Headrick_14-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Headrick_14-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHeadrick2002" class="citation journal cs1">Headrick, Michael (2002). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20091025120920/http://geocities.com/mvhw/anchor.html">"Origin and Evolution of the Anchor Clock Escapement"</a>. <i>Control Systems Magazine</i>. <b>22</b> (2). Inst. of Electrical and Electronic Engineers. Archived from <a rel="nofollow" class="external text" href="http://www.geocities.com/mvhw/anchor.html">the original</a> on October 25, 2009<span class="reference-accessdate">. Retrieved <span class="nowrap">2007-06-06</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Control+Systems+Magazine&rft.atitle=Origin+and+Evolution+of+the+Anchor+Clock+Escapement&rft.volume=22&rft.issue=2&rft.date=2002&rft.aulast=Headrick&rft.aufirst=Michael&rft_id=http%3A%2F%2Fwww.geocities.com%2Fmvhw%2Fanchor.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Usher-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-Usher_15-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFUsher2013" class="citation book cs1">Usher, Abbott Payson (2013). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Zt4Aw9wKjm8C&q=escapement&pg=PA193"><i>A History of Mechanical Inventions</i></a>. Courier Dover Publications. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-486-14359-0" title="Special:BookSources/978-0-486-14359-0"><bdi>978-0-486-14359-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+History+of+Mechanical+Inventions&rft.pub=Courier+Dover+Publications&rft.date=2013&rft.isbn=978-0-486-14359-0&rft.aulast=Usher&rft.aufirst=Abbott+Payson&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DZt4Aw9wKjm8C%26q%3Descapement%26pg%3DPA193&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Scheller-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-Scheller_16-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFScheller1995" class="citation book cs1">Scheller, Robert Walter (1995). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=LoFaBMJVeMYC&q=%22escapement&pg=PA185"><i>Exemplum: Model-book Drawings and the Practice of Artistic Transmission in the Middle Ages (ca. 900-ca. 1470)</i></a>. Amsterdam University Press. p. 185. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/90-5356-130-7" title="Special:BookSources/90-5356-130-7"><bdi>90-5356-130-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Exemplum%3A+Model-book+Drawings+and+the+Practice+of+Artistic+Transmission+in+the+Middle+Ages+%28ca.+900-ca.+1470%29&rft.pages=185&rft.pub=Amsterdam+University+Press&rft.date=1995&rft.isbn=90-5356-130-7&rft.aulast=Scheller&rft.aufirst=Robert+Walter&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DLoFaBMJVeMYC%26q%3D%2522escapement%26pg%3DPA185&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span>, footnote 7</span> </li> <li id="cite_note-Barnes-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-Barnes_17-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBarnes2009" class="citation book cs1">Barnes, Carl F. (2009). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=SJ0YkdmqRMcC&q=%22escapement&pg=PA159"><i>The Portfolio of Villard de Honnecourt (Paris, Bibliothèque Nationale de France, MS Fr 19093)</i></a>. Ashgate Publishing Ltd. p. 159. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7546-5102-4" title="Special:BookSources/978-0-7546-5102-4"><bdi>978-0-7546-5102-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Portfolio+of+Villard+de+Honnecourt+%28Paris%2C+Biblioth%C3%A8que+Nationale+de+France%2C+MS+Fr+19093%29&rft.pages=159&rft.pub=Ashgate+Publishing+Ltd.&rft.date=2009&rft.isbn=978-0-7546-5102-4&rft.aulast=Barnes&rft.aufirst=Carl+F.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DSJ0YkdmqRMcC%26q%3D%2522escapement%26pg%3DPA159&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Wang-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-Wang_18-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeedhamWangde_Solla_Price1986" class="citation book cs1">Needham, Joseph; Wang, Ling; de Solla Price, Derek John (1986). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=bCA9AAAAIAAJ&q=%22villard+de+honnecourt%22+escapement&pg=PA195"><i>Heavenly Clockwork: The Great Astronomical Clocks of Medieval China</i></a>. CUP Archive. p. 195. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-32276-6" title="Special:BookSources/0-521-32276-6"><bdi>0-521-32276-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Heavenly+Clockwork%3A+The+Great+Astronomical+Clocks+of+Medieval+China&rft.pages=195&rft.pub=CUP+Archive&rft.date=1986&rft.isbn=0-521-32276-6&rft.aulast=Needham&rft.aufirst=Joseph&rft.au=Wang%2C+Ling&rft.au=de+Solla+Price%2C+Derek+John&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DbCA9AAAAIAAJ%26q%3D%2522villard%2Bde%2Bhonnecourt%2522%2Bescapement%26pg%3DPA195&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span>, footnote 3</span> </li> <li id="cite_note-Needham-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-Needham_19-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeedham1965" class="citation book cs1">Needham, Joseph (1965). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=SeGyrCfYs2AC&q=%22villard+de+honnecourt%22+escapement&pg=PA443"><i>Science and Civilisation in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering</i></a>. Cambridge University Press. p. 443. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-05803-1" title="Special:BookSources/0-521-05803-1"><bdi>0-521-05803-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Science+and+Civilisation+in+China%3A+Volume+4%2C+Physics+and+Physical+Technology%2C+Part+2%2C+Mechanical+Engineering&rft.pages=443&rft.pub=Cambridge+University+Press&rft.date=1965&rft.isbn=0-521-05803-1&rft.aulast=Needham&rft.aufirst=Joseph&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DSeGyrCfYs2AC%26q%3D%2522villard%2Bde%2Bhonnecourt%2522%2Bescapement%26pg%3DPA443&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-White-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-White_20-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFWhite1964">White 1964</a>, p. 173</span> </li> <li id="cite_note-Rossum-21"><span class="mw-cite-backlink">^ <a href="#cite_ref-Rossum_21-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Rossum_21-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDohrn-van_Rossum1996" class="citation book cs1">Dohrn-van Rossum, Gerhard (1996). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=9Za4jdBEVB4C&q=%22villard+de+honnecourt%22+escapement&pg=PA105"><i>History of the Hour: Clocks and Modern Temporal Orders</i></a>. University of Chicago Press. pp. <span class="nowrap">105–</span>106. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-226-15510-2" title="Special:BookSources/0-226-15510-2"><bdi>0-226-15510-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=History+of+the+Hour%3A+Clocks+and+Modern+Temporal+Orders&rft.pages=%3Cspan+class%3D%22nowrap%22%3E105-%3C%2Fspan%3E106&rft.pub=University+of+Chicago+Press&rft.date=1996&rft.isbn=0-226-15510-2&rft.aulast=Dohrn-van+Rossum&rft.aufirst=Gerhard&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D9Za4jdBEVB4C%26q%3D%2522villard%2Bde%2Bhonnecourt%2522%2Bescapement%26pg%3DPA105&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><a href="#CITEREFWhite1964">White 1964</a>, pp. 126–127</span> </li> <li id="cite_note-Whitrow-23"><span class="mw-cite-backlink">^ <a href="#cite_ref-Whitrow_23-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Whitrow_23-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Whitrow_23-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Whitrow_23-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Whitrow_23-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Whitrow_23-5"><sup><i><b>f</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWhitrow1989" class="citation book cs1">Whitrow, G. J. (1989). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=o8Nb5KLBxVQC&pg=PA104"><i>Time in History: Views of Time from Prehistory to the Present Day</i></a>. Oxford Univ. Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-19-285211-6" title="Special:BookSources/0-19-285211-6"><bdi>0-19-285211-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Time+in+History%3A+Views+of+Time+from+Prehistory+to+the+Present+Day&rft.pub=Oxford+Univ.+Press&rft.date=1989&rft.isbn=0-19-285211-6&rft.aulast=Whitrow&rft.aufirst=G.+J.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Do8Nb5KLBxVQC%26pg%3DPA104&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><a href="#CITEREFWhite1964">White 1964</a>, pp. 119–127</span> </li> <li id="cite_note-Cipolla2004-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-Cipolla2004_25-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCipolla2004" class="citation book cs1">Cipolla, Carlo M. (2004). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=YSf9MVxa2JEC&q=verge+escapement+technology&pg=PA31"><i>Clocks and Culture, 1300 to 1700</i></a>. W.W. Norton & Co. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-393-32443-5" title="Special:BookSources/0-393-32443-5"><bdi>0-393-32443-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Clocks+and+Culture%2C+1300+to+1700&rft.pub=W.W.+Norton+%26+Co.&rft.date=2004&rft.isbn=0-393-32443-5&rft.aulast=Cipolla&rft.aufirst=Carlo+M.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DYSf9MVxa2JEC%26q%3Dverge%2Bescapement%2Btechnology%26pg%3DPA31&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span>, p.31</span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><a href="#CITEREFWhite1964">White 1964</a>, p. 124</span> </li> <li id="cite_note-North2-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-North2_27-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNorth2005" class="citation book cs1">North, John David (2005). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=rAuj1_x34XoC&pg=PR175"><i>God's Clockmaker: Richard of Wallingford and the Invention of Time</i></a>. UK: Hambledon & London. pp. <span class="nowrap">175–</span>183. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-85285-451-0" title="Special:BookSources/1-85285-451-0"><bdi>1-85285-451-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=God%27s+Clockmaker%3A+Richard+of+Wallingford+and+the+Invention+of+Time&rft.place=UK&rft.pages=%3Cspan+class%3D%22nowrap%22%3E175-%3C%2Fspan%3E183&rft.pub=Hambledon+%26+London&rft.date=2005&rft.isbn=1-85285-451-0&rft.aulast=North&rft.aufirst=John+David&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DrAuj1_x34XoC%26pg%3DPR175&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDohrn-van_Rossum1996" class="citation book cs1">Dohrn-van Rossum, Gerhard (1996). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=xYhlNoUu-toC&q=verge+escapement+technology"><i>History of the Hour: Clocks and Modern Temporal Orders</i></a>. Univ. of Chicago Press. pp. <span class="nowrap">50–</span>52. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-226-15511-0" title="Special:BookSources/0-226-15511-0"><bdi>0-226-15511-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=History+of+the+Hour%3A+Clocks+and+Modern+Temporal+Orders&rft.pages=%3Cspan+class%3D%22nowrap%22%3E50-%3C%2Fspan%3E52&rft.pub=Univ.+of+Chicago+Press&rft.date=1996&rft.isbn=0-226-15511-0&rft.aulast=Dohrn-van+Rossum&rft.aufirst=Gerhard&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DxYhlNoUu-toC%26q%3Dverge%2Bescapement%2Btechnology&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-NIST2-29"><span class="mw-cite-backlink">^ <a href="#cite_ref-NIST2_29-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-NIST2_29-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.nist.gov/pml/time-and-frequency-division/popular-links/walk-through-time/walk-through-time-revolution">"A Revolution in Timekeeping"</a>. <i>A Walk Through Time</i>. <a href="/wiki/National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a>. 2004<span class="reference-accessdate">. Retrieved <span class="nowrap">2022-10-13</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=A+Walk+Through+Time&rft.atitle=A+Revolution+in+Timekeeping&rft.date=2004&rft_id=https%3A%2F%2Fwww.nist.gov%2Fpml%2Ftime-and-frequency-division%2Fpopular-links%2Fwalk-through-time%2Fwalk-through-time-revolution&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><a href="#CITEREFMilham1945">Milham 1945</a>, p. 180</span> </li> <li id="cite_note-Rawlings-31"><span class="mw-cite-backlink">^ <a href="#cite_ref-Rawlings_31-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Rawlings_31-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a href="#CITEREFRawlings1993">Rawlings 1993</a></span> </li> <li id="cite_note-Jones2000-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-Jones2000_32-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJones2000" class="citation book cs1">Jones, Tony (2000). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=krZBQbnHTY0C&pg=PA30"><i>Splitting the Second: The Story of Atomic Time</i></a>. CRC Press. p. 30. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-7503-0640-8" title="Special:BookSources/0-7503-0640-8"><bdi>0-7503-0640-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Splitting+the+Second%3A+The+Story+of+Atomic+Time&rft.pages=30&rft.pub=CRC+Press&rft.date=2000&rft.isbn=0-7503-0640-8&rft.aulast=Jones&rft.aufirst=Tony&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DkrZBQbnHTY0C%26pg%3DPA30&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKaler2002" class="citation book cs1">Kaler, James B. (2002). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=KYLSMsduNqcC&pg=PA183"><i>Ever-changing Sky: A Guide to the Celestial Sphere</i></a>. UK: Cambridge Univ. Press. p. 183. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-49918-6" title="Special:BookSources/0-521-49918-6"><bdi>0-521-49918-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Ever-changing+Sky%3A+A+Guide+to+the+Celestial+Sphere&rft.place=UK&rft.pages=183&rft.pub=Cambridge+Univ.+Press&rft.date=2002&rft.isbn=0-521-49918-6&rft.aulast=Kaler&rft.aufirst=James+B.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DKYLSMsduNqcC%26pg%3DPA183&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHall1996" class="citation web cs1">Hall, E. T. (1996). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071224123113/http://www.iinet.com/~holmstro/hsn_article.php">"The Littlemore Clock"</a>. <i>NAWCC Chapter 161 - Horological Science</i>. National Association of Watch and Clock Collectors. Archived from <a rel="nofollow" class="external text" href="http://www.iinet.com/~holmstro/hsn_article.php">the original</a> on 2007-12-24.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=NAWCC+Chapter+161+-+Horological+Science&rft.atitle=The+Littlemore+Clock&rft.date=1996&rft.aulast=Hall&rft.aufirst=E.+T.&rft_id=http%3A%2F%2Fwww.iinet.com%2F~holmstro%2Fhsn_article.php&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><a href="#CITEREFMilham1945">Milham 1945</a>, p. 180</span> </li> <li id="cite_note-Day-36"><span class="mw-cite-backlink">^ <a href="#cite_ref-Day_36-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Day_36-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Day_36-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Day_36-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text">"Jost Burgi" in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLance_Day_and_Ian_McNeil1996" class="citation book cs1">Lance Day and Ian McNeil, ed. (1996). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=m8TsygLyfSMC&pg=PA205"><i>Biographical dictionary of the history of technology</i></a>. <a href="/wiki/Routledge" title="Routledge">Routledge</a> (Routledge Reference). p. 116. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-134-65020-5" title="Special:BookSources/1-134-65020-5"><bdi>1-134-65020-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Biographical+dictionary+of+the+history+of+technology&rft.pages=116&rft.pub=Routledge+%28Routledge+Reference%29&rft.date=1996&rft.isbn=1-134-65020-5&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dm8TsygLyfSMC%26pg%3DPA205&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBritten1896" class="citation book cs1">Britten, Frederick J. (1896). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=5SYJAAAAIAAJ&pg=PA108"><i>Watch and Clockmaker's Handbook, 9th Edition</i></a>. E.F.& N. Spon. p. 108.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Watch+and+Clockmaker%27s+Handbook%2C+9th+Edition&rft.pages=108&rft.pub=E.F.%26+N.+Spon&rft.date=1896&rft.aulast=Britten&rft.aufirst=Frederick+J.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D5SYJAAAAIAAJ%26pg%3DPA108&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-38"><span class="mw-cite-backlink"><b><a href="#cite_ref-38">^</a></b></span> <span class="reference-text">Smith, Alan (2000) <a rel="nofollow" class="external text" href="http://www.mikeoates.org/mas/history/lectures/20001116.htm">The Towneley Clocks at Greenwich Observatory</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080705091441/http://www.mikeoates.org/mas/history/lectures/20001116.htm">Archived</a> 2008-07-05 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> Retrieved 16 November 2007</span> </li> <li id="cite_note-39"><span class="mw-cite-backlink"><b><a href="#cite_ref-39">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFlamsteedForbesMurdin1995" class="citation book cs1">Flamsteed, John; Forbes, Eric; Murdin, Lesley (1995). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Hrm9aCi48CYC&pg=PA376"><i>The Correspondence of John Flamsteed, First Astronomer Royal, Vol.1</i></a>. CRC Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7503-0147-3" title="Special:BookSources/978-0-7503-0147-3"><bdi>978-0-7503-0147-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Correspondence+of+John+Flamsteed%2C+First+Astronomer+Royal%2C+Vol.1&rft.pub=CRC+Press&rft.date=1995&rft.isbn=978-0-7503-0147-3&rft.aulast=Flamsteed&rft.aufirst=John&rft.au=Forbes%2C+Eric&rft.au=Murdin%2C+Lesley&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DHrm9aCi48CYC%26pg%3DPA376&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span> Letter 229 Flamsteed to Towneley (September 22, 1675), p.374, and Annotation 11 p.375</span> </li> <li id="cite_note-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-40">^</a></b></span> <span class="reference-text">Andrewes, W.J.H. <a rel="nofollow" class="external text" href="https://books.google.com/books?id=F7wNQk219KMC&pg=PA126&sig=v3OGcBZ9yAuEx-hfdTfUWnBfiFQ"><i>Clocks and Watches: The leap to precision</i></a> in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMacey1994" class="citation book cs1">Macey, Samuel (1994). <i>Encyclopedia of Time</i>. Taylor & Francis. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-8153-0615-6" title="Special:BookSources/0-8153-0615-6"><bdi>0-8153-0615-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Encyclopedia+of+Time&rft.pub=Taylor+%26+Francis&rft.date=1994&rft.isbn=0-8153-0615-6&rft.aulast=Macey&rft.aufirst=Samuel&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span> p.126, this cites a letter of December 11, but he may have meant the September 22 letter mentioned above.</span> </li> <li id="cite_note-41"><span class="mw-cite-backlink"><b><a href="#cite_ref-41">^</a></b></span> <span class="reference-text"><a href="#CITEREFMilham1945">Milham 1945</a>, p. 185</span> </li> <li id="cite_note-42"><span class="mw-cite-backlink"><b><a href="#cite_ref-42">^</a></b></span> <span class="reference-text"><a href="#CITEREFMilham1945">Milham 1945</a>, p. 235</span> </li> <li id="cite_note-43"><span class="mw-cite-backlink"><b><a href="#cite_ref-43">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJaquetChapuis1970" class="citation book cs1">Jaquet, Eugène; Chapuis, Alfred (1970). <i>Technique and history of the Swiss watch</i>. London: Spring Books. p. 222. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-600-03633-3" title="Special:BookSources/978-0-600-03633-3"><bdi>978-0-600-03633-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Technique+and+history+of+the+Swiss+watch&rft.place=London&rft.pages=222&rft.pub=Spring+Books&rft.date=1970&rft.isbn=978-0-600-03633-3&rft.aulast=Jaquet&rft.aufirst=Eug%C3%A8ne&rft.au=Chapuis%2C+Alfred&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Betts-44"><span class="mw-cite-backlink">^ <a href="#cite_ref-Betts_44-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Betts_44-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBetts2006" class="citation book cs1">Betts, Jonathan (2006). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=XhwhoPOp1QMC&pg=PT461"><i>Time Restored:The Harrison timekeepers and R.T. Gould, the man who knew (almost) everything</i></a>. Oxford University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-19-856802-5" title="Special:BookSources/978-0-19-856802-5"><bdi>978-0-19-856802-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Time+Restored%3AThe+Harrison+timekeepers+and+R.T.+Gould%2C+the+man+who+knew+%28almost%29+everything&rft.pub=Oxford+University+Press&rft.date=2006&rft.isbn=978-0-19-856802-5&rft.aulast=Betts&rft.aufirst=Jonathan&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DXhwhoPOp1QMC%26pg%3DPT461&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Macey-45"><span class="mw-cite-backlink"><b><a href="#cite_ref-Macey_45-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMacey1994" class="citation book cs1">Macey, Samuel L. (1994). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=F7wNQk219KMC&pg=PA348"><i>Encyclopedia of Time</i></a>. Garland Publishing. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-8153-0615-6" title="Special:BookSources/0-8153-0615-6"><bdi>0-8153-0615-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Encyclopedia+of+Time&rft.pub=Garland+Publishing&rft.date=1994&rft.isbn=0-8153-0615-6&rft.aulast=Macey&rft.aufirst=Samuel+L.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DF7wNQk219KMC%26pg%3DPA348&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-46"><span class="mw-cite-backlink"><b><a href="#cite_ref-46">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=s-cOAAAAQAAJ&pg=PA122"><i>Britten's Watch & Clock Makers' Handbook Dictionary & Guide Fifteenth Edition</i></a>. Taylor & Francis. p. 122.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Britten%27s+Watch+%26+Clock+Makers%27+Handbook+Dictionary+%26+Guide+Fifteenth+Edition&rft.pages=122&rft.pub=Taylor+%26+Francis&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Ds-cOAAAAQAAJ%26pg%3DPA122&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-47"><span class="mw-cite-backlink"><b><a href="#cite_ref-47">^</a></b></span> <span class="reference-text"><a href="#CITEREFMilham1945">Milham 1945</a>, p. 272</span> </li> <li id="cite_note-Britten-48"><span class="mw-cite-backlink">^ <a href="#cite_ref-Britten_48-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Britten_48-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Britten_48-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Britten_48-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBritten1896" class="citation book cs1">Britten, Frederick James (1896). <a rel="nofollow" class="external text" href="https://archive.org/details/watchclockmaker01britgoog"><i>The Watch & Clock Makers' Handbook, Dictionary and Guide</i></a> (9 ed.). London: E. F. and N. Spon Ltd. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/watchclockmaker01britgoog/page/n104">98</a>–101. <q>cylinder escapement.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Watch+%26+Clock+Makers%27+Handbook%2C+Dictionary+and+Guide&rft.place=London&rft.pages=98-101&rft.edition=9&rft.pub=E.+F.+and+N.+Spon+Ltd.&rft.date=1896&rft.aulast=Britten&rft.aufirst=Frederick+James&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fwatchclockmaker01britgoog&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Du1-49"><span class="mw-cite-backlink">^ <a href="#cite_ref-Du1_49-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Du1_49-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Du1_49-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDuXie2012" class="citation book cs1">Du, Ruxu; Xie, Longhan (2012). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=fMyRkbXI5fcC&q=%22cylinder+escapement&pg=PA26"><i>The Mechanics of Mechanical Watches and Clocks</i></a>. Springer. pp. <span class="nowrap">26–</span>29. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3-642-29308-5" title="Special:BookSources/978-3-642-29308-5"><bdi>978-3-642-29308-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Mechanics+of+Mechanical+Watches+and+Clocks&rft.pages=%3Cspan+class%3D%22nowrap%22%3E26-%3C%2Fspan%3E29&rft.pub=Springer&rft.date=2012&rft.isbn=978-3-642-29308-5&rft.aulast=Du&rft.aufirst=Ruxu&rft.au=Xie%2C+Longhan&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DfMyRkbXI5fcC%26q%3D%2522cylinder%2Bescapement%26pg%3DPA26&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Nelthropp_1873-50"><span class="mw-cite-backlink">^ <a href="#cite_ref-Nelthropp_1873_50-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Nelthropp_1873_50-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNelthropp1873" class="citation book cs1">Nelthropp, Harry Leonard (1873). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=7DcDAAAAQAAJ&pg=PA159"><i>A Treatise on Watchwork, Past and Present</i></a>. E. & F.N. Spon.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Treatise+on+Watchwork%2C+Past+and+Present&rft.pub=E.+%26+F.N.+Spon&rft.date=1873&rft.aulast=Nelthropp&rft.aufirst=Harry+Leonard&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D7DcDAAAAQAAJ%26pg%3DPA159&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span>, p.159-164.</span> </li> <li id="cite_note-51"><span class="mw-cite-backlink"><b><a href="#cite_ref-51">^</a></b></span> <span class="reference-text">Reid's Treatise 2nd Edition p. 240</span> </li> <li id="cite_note-52"><span class="mw-cite-backlink"><b><a href="#cite_ref-52">^</a></b></span> <span class="reference-text">British patent no. 1811</span> </li> <li id="cite_note-Glasgow1885-53"><span class="mw-cite-backlink">^ <a href="#cite_ref-Glasgow1885_53-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Glasgow1885_53-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Glasgow1885_53-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGlasgow1885" class="citation book cs1">Glasgow, David (1885). <a rel="nofollow" class="external text" href="https://archive.org/details/watchandclockma00glasgoog"><i>Watch and Clock Making</i></a>. London: Cassel & Co. p. <a rel="nofollow" class="external text" href="https://archive.org/details/watchandclockma00glasgoog/page/n123">137</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Watch+and+Clock+Making&rft.place=London&rft.pages=137&rft.pub=Cassel+%26+Co.&rft.date=1885&rft.aulast=Glasgow&rft.aufirst=David&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fwatchandclockma00glasgoog&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span>, p137-154</span> </li> <li id="cite_note-54"><span class="mw-cite-backlink"><b><a href="#cite_ref-54">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMundy2007" class="citation web cs1">Mundy, Oliver (June 2007). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071013214035/http://horologia.co.uk/escapements.html">"Watch Escapements"</a>. <i>The Watch Cabinet</i>. 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In <a href="/wiki/Hugh_Chisholm" title="Hugh Chisholm">Chisholm, Hugh</a> (ed.). <i><a href="/wiki/Encyclop%C3%A6dia_Britannica_Eleventh_Edition" title="Encyclopædia Britannica Eleventh Edition">Encyclopædia Britannica</a></i>. Vol. 28 (11th ed.). Cambridge University Press. pp. <span class="nowrap">362–</span>366, see end of page 363. <q>The duplex escapement....</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Watch&rft.btitle=Encyclop%C3%A6dia+Britannica&rft.pages=%3Cspan+class%3D%22nowrap%22%3E362-%3C%2Fspan%3E366%2C+see+end+of+page+363&rft.edition=11th&rft.pub=Cambridge+University+Press&rft.date=1911&rft.aulast=Beckett&rft.aufirst=Edmund&rft.au=Cunynghame%2C+Henry+Hardinge&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-60"><span class="mw-cite-backlink"><b><a href="#cite_ref-60">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://nawcc.pastperfectonline.com/webobject/FB1B504C-A7D1-428A-9015-338166254525">"Wristwatch - 76.2.109 | National Watch & Clock Museum"</a>. <i>nawcc.pastperfectonline.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2024-02-08</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=nawcc.pastperfectonline.com&rft.atitle=Wristwatch+-+76.2.109+%7C+National+Watch+%26+Clock+Museum&rft_id=https%3A%2F%2Fnawcc.pastperfectonline.com%2Fwebobject%2FFB1B504C-A7D1-428A-9015-338166254525&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Du2-61"><span class="mw-cite-backlink">^ <a href="#cite_ref-Du2_61-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Du2_61-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDuXie2012" class="citation book cs1">Du, Ruxu; Xie, Longhan (2012). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=fMyRkbXI5fcC&q=%22grasshopper+escapement%22&pg=PA19"><i>The Mechanics of Mechanical Watches and Clocks</i></a>. Springer Science and Business Media. pp. <span class="nowrap">17–</span>19. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3-642-29308-5" title="Special:BookSources/978-3-642-29308-5"><bdi>978-3-642-29308-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Mechanics+of+Mechanical+Watches+and+Clocks&rft.pages=%3Cspan+class%3D%22nowrap%22%3E17-%3C%2Fspan%3E19&rft.pub=Springer+Science+and+Business+Media&rft.date=2012&rft.isbn=978-3-642-29308-5&rft.aulast=Du&rft.aufirst=Ruxu&rft.au=Xie%2C+Longhan&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DfMyRkbXI5fcC%26q%3D%2522grasshopper%2Bescapement%2522%26pg%3DPA19&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Britten2-62"><span class="mw-cite-backlink"><b><a href="#cite_ref-Britten2_62-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBritten1899" class="citation book cs1">Britten, Frederick James (1899). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=4e_eAAAAMAAJ&q=escapement+grasshopper&pg=PA216"><i>Old Clocks and Watches and their Makers</i></a>. London: B. T. Batsford. p. 216. <q>[Harrison's] escapement, called the 'grasshopper'... was of no practical value and need not be further described.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Old+Clocks+and+Watches+and+their+Makers&rft.place=London&rft.pages=216&rft.pub=B.+T.+Batsford&rft.date=1899&rft.aulast=Britten&rft.aufirst=Frederick+James&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D4e_eAAAAMAAJ%26q%3Descapement%2Bgrasshopper%26pg%3DPA216&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-63"><span class="mw-cite-backlink"><b><a href="#cite_ref-63">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://leapsecond.com/pend/clockb/">"Harrison / Burgess Clock B"</a>. <i>leapsecond.com</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=leapsecond.com&rft.atitle=Harrison+%2F+Burgess+Clock+B&rft_id=http%3A%2F%2Fleapsecond.com%2Fpend%2Fclockb%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-64"><span class="mw-cite-backlink"><b><a href="#cite_ref-64">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVan_Baak2015" class="citation conference cs1">Van Baak, Tom (April 2015). <a rel="nofollow" class="external text" href="http://leapsecond.com/pend/clockb/2015-tvb-Greenwich-ClockB-ppt.pdf"><i>A close look at clock A close look at clock 'B': and why pendulum clocks are even more interesting than atomic clocks</i></a> <span class="cs1-format">(PDF)</span>. Harrison Decoded Conference. Greenwich.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.btitle=A+close+look+at+clock+A+close+look+at+clock+%27B%27%3A+and+why+pendulum+clocks+are+even+more+interesting+than+atomic+clocks&rft.place=Greenwich&rft.date=2015-04&rft.aulast=Van+Baak&rft.aufirst=Tom&rft_id=http%3A%2F%2Fleapsecond.com%2Fpend%2Fclockb%2F2015-tvb-Greenwich-ClockB-ppt.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-65"><span class="mw-cite-backlink"><b><a href="#cite_ref-65">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLove2016" class="citation magazine cs1">Love, Shayla (Jan 19, 2016). <a rel="nofollow" class="external text" href="https://www.theatlantic.com/technology/archive/2016/01/pendulum-clock-john-harrison/424614">"Building an Impossible Clock"</a>. <i>The Atlantic</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Atlantic&rft.atitle=Building+an+Impossible+Clock&rft.date=2016-01-19&rft.aulast=Love&rft.aufirst=Shayla&rft_id=https%3A%2F%2Fwww.theatlantic.com%2Ftechnology%2Farchive%2F2016%2F01%2Fpendulum-clock-john-harrison%2F424614&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-66"><span class="mw-cite-backlink"><b><a href="#cite_ref-66">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDaniels" class="citation web cs1">Daniels, George. <a rel="nofollow" class="external text" href="http://www.danielslondon.com/">"About George Daniels"</a>. <i>Daniels London</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2008-06-12</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Daniels+London&rft.atitle=About+George+Daniels&rft.aulast=Daniels&rft.aufirst=George&rft_id=http%3A%2F%2Fwww.danielslondon.com%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-67"><span class="mw-cite-backlink"><b><a href="#cite_ref-67">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFThompson2001" class="citation web cs1">Thompson, Curtis (2001). <a rel="nofollow" class="external text" href="http://home.xnet.com/~cmaddox/daniels_co-ax.html">"Where George Daniels shopped the Co-Axial..."</a> [Chuck Maddox home page]<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-06-12</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Where+George+Daniels+shopped+the+Co-Axial...&rft.pub=%5BChuck+Maddox+home+page%5D&rft.date=2001&rft.aulast=Thompson&rft.aufirst=Curtis&rft_id=http%3A%2F%2Fhome.xnet.com%2F~cmaddox%2Fdaniels_co-ax.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span> 17 June 2001 Addendum</span> </li> <li id="cite_note-68"><span class="mw-cite-backlink"><b><a href="#cite_ref-68">^</a></b></span> <span class="reference-text">Charles Gros 'Echappements' 1914 P.174</span> </li> <li id="cite_note-69"><span class="mw-cite-backlink"><b><a href="#cite_ref-69">^</a></b></span> <span class="reference-text">'English and American watches' George Daniels Published 1967</span> </li> <li id="cite_note-70"><span class="mw-cite-backlink"><b><a href="#cite_ref-70">^</a></b></span> <span class="reference-text">Chamberlain 'It's About Time' Pages 428-429, also P.93 which shows a diagrammatic view of the escapement. Chamberlain 1978 Reprint <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0%2B900470%2B81X" title="Special:BookSources/0+900470+81X">0 900470 81X</a></span> </li> <li id="cite_note-71"><span class="mw-cite-backlink"><b><a href="#cite_ref-71">^</a></b></span> <span class="reference-text">Gros Echappements 1914 P.184 Fig.213</span> </li> <li id="cite_note-72"><span class="mw-cite-backlink"><b><a href="#cite_ref-72">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNicolet1999" class="citation web cs1">Nicolet, J.C. (1999). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100421085157/http://www.europastar.com/europastar/watch_tech/nicolet8.jsp">"Could you explain the mechanism of the coaxial watch?"</a>. <i>Questions in Time</i>. Europa star online. Archived from <a rel="nofollow" class="external text" href="http://www.europastar.com/europastar/watch_tech/nicolet8.jsp">the original</a> on 2010-04-21<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-06-12</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Questions+in+Time&rft.atitle=Could+you+explain+the+mechanism+of+the+coaxial+watch%3F&rft.date=1999&rft.aulast=Nicolet&rft.aufirst=J.C.&rft_id=http%3A%2F%2Fwww.europastar.com%2Feuropastar%2Fwatch_tech%2Fnicolet8.jsp&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-Maddox-73"><span class="mw-cite-backlink">^ <a href="#cite_ref-Maddox_73-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Maddox_73-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOdets1999" class="citation web cs1">Odets, Walt (1999). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080611094453/http://www.timezone.com/library/horologium/horologium631670193290479607">"The Omega Coaxial: An impressive achievement"</a>. <i>The Horologium</i>. TimeZone.com. Archived from <a rel="nofollow" class="external text" href="http://www.timezone.com/library/horologium/horologium631670193290479607">the original</a> on 2008-06-11<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-06-12</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Horologium&rft.atitle=The+Omega+Coaxial%3A+An+impressive+achievement&rft.date=1999&rft.aulast=Odets&rft.aufirst=Walt&rft_id=http%3A%2F%2Fwww.timezone.com%2Flibrary%2Fhorologium%2Fhorologium631670193290479607&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-74"><span class="mw-cite-backlink"><b><a href="#cite_ref-74">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDéhon1999" class="citation web cs1">Déhon, Nicolas (December 16, 1999). <a rel="nofollow" class="external text" href="https://patents.google.com/patent/EP3599514A1/en?inventor=D%C3%A9hon%2c+Nicolas&oq=D%C3%A9hon%2c+Nicolas">"Exhaust mechanism having bistable and monostable springs"</a>. <i>Google Patents</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Google+Patents&rft.atitle=Exhaust+mechanism+having+bistable+and+monostable+springs&rft.date=1999-12-16&rft.aulast=D%C3%A9hon&rft.aufirst=Nicolas&rft_id=https%3A%2F%2Fpatents.google.com%2Fpatent%2FEP3599514A1%2Fen%3Finventor%3DD%25C3%25A9hon%252c%2BNicolas%26oq%3DD%25C3%25A9hon%252c%2BNicolas&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-75"><span class="mw-cite-backlink"><b><a href="#cite_ref-75">^</a></b></span> <span class="reference-text">Monochrome-watches, <a rel="nofollow" class="external text" href="https://monochrome-watches.com/a-technical-perspective-the-evolution-of-the-escapement-and-recent-innovations">"The evolution of the escapement and recent innovations"</a>, February 2016</span> </li> <li id="cite_note-76"><span class="mw-cite-backlink"><b><a href="#cite_ref-76">^</a></b></span> <span class="reference-text">Hipp, Matth.(aeus): Sich selbst controlirende Uhr, welche augenbliklich anzeigt, wenn die durch Reibung etc. verursachte Unregelmäßigkeit im Gang auch nur den tausendsten Theil einer Secunde ausmacht und welche ein mehr als hundertfach größeres Hinderniß überwindet, ehe sie stehen bleibt, als andere Uhren, in: Polytechnisches Journal 88, 1843, p. 258-264, 441-446, sheet IV and V</span> </li> <li id="cite_note-77"><span class="mw-cite-backlink"><b><a href="#cite_ref-77">^</a></b></span> <span class="reference-text">French patent for an electrical driven pendulum clock with hipp-toggle, May 27, 1863: "Pendule ou horloge électro-magnétique à appal direct d'électricité" - The evolution of the hipp-toggle is described by: Johannes Graf: Der lange Weg zur Hipp-Wippe. Ab wann werden Uhren von matthaeus Hipp elektrisch angetrieben? In: Chronométrophilia No. 76, 2014, p. 67-77.</span> </li> <li id="cite_note-78"><span class="mw-cite-backlink"><b><a href="#cite_ref-78">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://clockdoc.org/default.aspx?aid=80">ClockDoc. The Electric Clock Archive</a></span> </li> <li id="cite_note-79"><span class="mw-cite-backlink"><b><a href="#cite_ref-79">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHope-Jones" class="citation book cs1">Hope-Jones, Frank. <i>Electric Clocks</i>. N.A.G. 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Retrieved <span class="nowrap">2020-05-30</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+University+of+Queensland+-+Physics+Museum&rft.atitle=Synchronome+Master+Clock+%28circa+1955%29&rft_id=https%3A%2F%2Fphysicsmuseum.uq.edu.au%2Fsynchronome-master-clock-0&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> <li id="cite_note-81"><span class="mw-cite-backlink"><b><a href="#cite_ref-81">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.electric-clocks.nl/clocks/en/page10.htm">"Electric clocks – a history through animation"</a>. <i>electric-clocks.nl</i>. 2010<span class="reference-accessdate">. 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Retrieved <span class="nowrap">November 10,</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=hua.umf.maine.edu&rft.atitle=Synchronome+-+%E4%B8%AD%E5%9B%BD%E5%A4%A9%E6%96%87%E5%AD%A6+-+%E4%B8%A4%E5%8F%B0%E6%91%86%E7%9A%84%E7%94%B5%E5%AD%90%E9%92%9F+Chinese+Astronomy&rft.date=2007-09&rft.au=Marilyn+Shea&rft_id=http%3A%2F%2Fhua.umf.maine.edu%2FChina%2Fastronomy%2Ftianpage%2F0040h_synchronome6745w.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=27" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBritten1881" class="citation book cs1">Britten, Frederick J. (1881). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=jc0AAAAAMAAJ"><i>The Watch and Clockmaker's Handbook, 4th Ed</i></a>. London: W. Kent & Co.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Watch+and+Clockmaker%27s+Handbook%2C+4th+Ed.&rft.place=London&rft.pub=W.+Kent+%26+Co.&rft.date=1881&rft.aulast=Britten&rft.aufirst=Frederick+J.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Djc0AAAAAMAAJ&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span>, p. 56-58</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBeckettCunynghame1911" class="citation encyclopaedia cs1">Beckett, Edmund; Cunynghame, Henry Hardinge (1911). <span class="cs1-ws-icon" title="s:1911 Encyclopædia Britannica/Watch"><a class="external text" href="https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Watch">"Watch" </a></span>. In <a href="/wiki/Hugh_Chisholm" title="Hugh Chisholm">Chisholm, Hugh</a> (ed.). <i><a href="/wiki/Encyclop%C3%A6dia_Britannica_Eleventh_Edition" title="Encyclopædia Britannica Eleventh Edition">Encyclopædia Britannica</a></i>. Vol. 28 (11th ed.). Cambridge University Press. pp. <span class="nowrap">362–</span>366.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Watch&rft.btitle=Encyclop%C3%A6dia+Britannica&rft.pages=%3Cspan+class%3D%22nowrap%22%3E362-%3C%2Fspan%3E366&rft.edition=11th&rft.pub=Cambridge+University+Press&rft.date=1911&rft.aulast=Beckett&rft.aufirst=Edmund&rft.au=Cunynghame%2C+Henry+Hardinge&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGlasgow1885" class="citation book cs1">Glasgow, David (1885). <a rel="nofollow" class="external text" href="https://archive.org/details/watchandclockma00glasgoog"><i>Watch and Clock Making</i></a>. London: Cassel & Co. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/watchandclockma00glasgoog/page/n123">137</a>–154.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Watch+and+Clock+Making&rft.place=London&rft.pages=137-154&rft.pub=Cassel+%26+Co.&rft.date=1885&rft.aulast=Glasgow&rft.aufirst=David&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fwatchandclockma00glasgoog&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMilham1945" class="citation book cs1">Milham, Willis I. (1945). <i>Time and Timekeepers</i>. New York: MacMillan. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-7808-0008-7" title="Special:BookSources/0-7808-0008-7"><bdi>0-7808-0008-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Time+and+Timekeepers&rft.place=New+York&rft.pub=MacMillan&rft.date=1945&rft.isbn=0-7808-0008-7&rft.aulast=Milham&rft.aufirst=Willis+I.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeedham1986" class="citation book cs1">Needham, Joseph (1986). <i>Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering</i>. Taipei: Caves Books Ltd.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Science+and+Civilization+in+China%3A+Volume+4%2C+Physics+and+Physical+Technology%2C+Part+2%2C+Mechanical+Engineering&rft.place=Taipei&rft.pub=Caves+Books+Ltd&rft.date=1986&rft.aulast=Needham&rft.aufirst=Joseph&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRawlings1993" class="citation book cs1">Rawlings, Arthur Lionel (1993). <i>The Science of Clocks and Watches, 3rd Ed</i>. Upton, UK: The British Horological Institute. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-9509621-3-9" title="Special:BookSources/0-9509621-3-9"><bdi>0-9509621-3-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Science+of+Clocks+and+Watches%2C+3rd+Ed.&rft.place=Upton%2C+UK&rft.pub=The+British+Horological+Institute&rft.date=1993&rft.isbn=0-9509621-3-9&rft.aulast=Rawlings&rft.aufirst=Arthur+Lionel&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWhite1964" class="citation book cs1">White, Lynn Townsend (1964). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=xa7zPNkxswQC&q=escapement+%22villard+de+honnecourt&pg=PA"><i>Medieval Technology and Social Change</i></a>. Oxford Univ. Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-19-500266-0" title="Special:BookSources/0-19-500266-0"><bdi>0-19-500266-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Medieval+Technology+and+Social+Change&rft.pub=Oxford+Univ.+Press&rft.date=1964&rft.isbn=0-19-500266-0&rft.aulast=White&rft.aufirst=Lynn+Townsend&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dxa7zPNkxswQC%26q%3Descapement%2B%2522villard%2Bde%2Bhonnecourt%26pg%3DPA&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=28" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDenny2010" class="citation journal cs1">Denny, Mark (June 2010). "The Tourbillon and How It Works". <i>IEEE Control Systems Magazine</i>. <b>30</b> (3). <a href="/wiki/IEEE_Control_Systems_Society" class="mw-redirect" title="IEEE Control Systems Society">IEEE Control Systems Society</a>: <span class="nowrap">19–</span>99. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2FMCS.2010.936291">10.1109/MCS.2010.936291</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:24169789">24169789</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=IEEE+Control+Systems+Magazine&rft.atitle=The+Tourbillon+and+How+It+Works&rft.volume=30&rft.issue=3&rft.pages=%3Cspan+class%3D%22nowrap%22%3E19-%3C%2Fspan%3E99&rft.date=2010-06&rft_id=info%3Adoi%2F10.1109%2FMCS.2010.936291&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A24169789%23id-name%3DS2CID&rft.aulast=Denny&rft.aufirst=Mark&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEscapement" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Escapement&action=edit&section=29" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></a></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Escapements" class="extiw" title="commons:Category:Escapements">Escapements</a></span>.</div></div> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1235681985"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237033735"><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Wiktionary-logo-en-v2.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/40px-Wiktionary-logo-en-v2.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/60px-Wiktionary-logo-en-v2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/80px-Wiktionary-logo-en-v2.svg.png 2x" data-file-width="512" data-file-height="512" /></a></span></div> <div class="side-box-text plainlist">Look up <i><b><a href="https://en.wiktionary.org/wiki/Special:Search/escapement" class="extiw" title="wiktionary:Special:Search/escapement">escapement</a></b></i> in Wiktionary, the free dictionary.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://www.abbeyclock.com/escapement.html">Mark Headrick's horology page</a>, with animated pictures of many escapements</li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20050219011511/http://www.bhi.co.uk/hj/August04AoM.PDF">Performance Of The Daniels Coaxial Escapement</a>, <i>Horological Journal</i>, August 2004</li> <li><a rel="nofollow" class="external text" href="https://www.gutenberg.org/ebooks/17021">Watch and Clock Escapements</a>, <i>The Keystone</i> (magazine), 1904, via <a href="/wiki/Project_Gutenberg" title="Project Gutenberg">Project Gutenberg</a>: "A Complete Study in Theory and Practice of the Lever, Cylinder and Chronometer Escapements, Together with a Brief Account of the Origin and Evolution of the Escapement in Horology."</li> <li><a rel="nofollow" class="external text" href="http://www.freepatentsonline.com/5140565.html">US Patent number 5140565</a>, issued 23 March 1992, for a cycloidal pendulum similar to that of Huygens'</li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070310233344/http://www.findarticles.com/p/articles/mi_qn4158/is_20010816/ai_n14411695">findarticles.com</a>: Obituary of Professor Edward Hall, <i>The Independent</i> (London), 16 August 2001</li> <li><a rel="nofollow" class="external text" href="http://www.awi-net.org/">American Watchmakers-Clockmakers Institute</a>, non-profit trade association</li> <li><a rel="nofollow" class="external text" href="http://fhs.ch/en/">Federation of the Swiss Watch Industry FH</a>, watch industry trade association</li> <li><a rel="nofollow" class="external text" href="http://www.directorypatent.com/WO/1999ZZSLASHZZ064936.html/">Method for transmitting bursts of mechanical energy from a power source to an oscillating</a> <a rel="nofollow" class="external text" href="https://archive.today/20130629003450/http://www.directorypatent.com/WO/1999ZZSLASHZZ064936.html/">Archived</a> 2013-06-29 at <a href="/wiki/Archive.today" title="Archive.today">archive.today</a></li> <li><a rel="nofollow" class="external text" href="http://www.europastar.com/watch-knowledge/1004087457-mechanical-unlocking-alternative-escapements.html">Alternative Escapements</a>, <i>Europa Star</i>, September 2014</li> <li><a rel="nofollow" class="external text" href="https://monochrome-watches.com/a-technical-perspective-the-evolution-of-the-escapement-and-recent-innovations">Evolution of the escapement</a>, <i>Monochrome-watches, Xavier Markl</i>, February 2016</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist 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