National Maritime Museum Manuscripts : Drawing of turret clock escapement

Harrison, John

National Maritime Museum Manuscripts

<p style='text-align: justify;'>The following document contains a drawing of an escapement which was designed by the clockmaker John Harrison for a turret clock at Trinity College, Cambridge. Though designed by Harrison, the escapement was actually made by another clockmaker, William Smith, something which was far from unusual in the extensive sub-contracting system which was fundamental to the production of time-keeping devices in the eighteenth century.</p><p style='text-align: justify;'>In 1832, in his Treatise on Clock and Watch Making: Theoretical and Practical, Thomas Reid suggests that the main importance of Harrison's design of the escapement and turret clock was the way he incorporated the knowledge that complex technologies like pendulum clocks rely on routine repair and maintenance into his designs. Reid notes that 'the pallet arms were of brass, made so as to put in the power of clock-maker to take the pallets very easily out, when repairing was necessary'.</p><p style='text-align: justify;'>While by no means the singularly crucial component of clocks and timepieces in the eighteenth century, the various developments of escapements make up an important aspect of the history of the relationship between the Board of Longitude and the development of marine timekeepers. As can be seen in documents <a href='/view/'> RGO 14/26 ()</a> and <a href='/view/'> RGO 14/27 ()</a>, the issue of the genesis and effectiveness of the spring detent escapement was crucial to the claims made by the watchmakers John Arnold and Thomas Earnshaw to the Board of Longitude in the early nineteenth century.</p>. <p style='text-align: justify;'>Eóin Phillips<br />History and Philosophy of Science<br />University of Cambridge<br /></p>