image MS_243_11_001v
Image number: RS.16639
Credit: ©The Royal Society

Anchor escapement in Jonas Moore's clock


11 December 1675


John Flamsteed (1646-1719, British), Astronomer

Object type

Archive reference number

Manuscript page number

f11 p1v



height (page): 310mm
width (page): 198mm


Content object


Drawing (actual size) of an anchor escapement in a clock owned by Sir Jonas Moore, which John Flamsteed described to Richard Towneley for comment. The letter is dated 11 December 1675. Towneley and Moore were in discussion about improving the clock's accuracy by altering the design of the pallets, now known as the deadbeat escapement. Towneley's design of the deadbeat escapement was used in the clock made by Thomas Tompion that was commissioned for the Greenwich Observatory by Moore. The clock is now in London at the British Museum (1928,0607.1).

Object history

'by his order I tooke them out of the clock in his dining roome, and forceing the axis of the pallets into a peece of paper took the exact measure of it as I have here delineated, the diameter of the pallet wheele I measured and have drawne it of the same breadth. both sidewayes. and flat that you may the better understand the forme and how the pallets are applyed and playes upon it with the true shampher or bevel given to the teeth. and by this way Sir Jonas thinks theire is but little Checke given to the second finger hee commends it to your consideration and wee shall be glad to hear your opinion of it. [marginal note: the pallet wheel has 54 teeth].' (The Correspondence of John Flamsteed, the First Astronomer Royal, ed. by Eric G. Forbes, Lesley Murdin, and Frances Willmoth, 3 vols (Bristol: Institute of Physics, 1995-2002), I, 385-87 (no. 234) (p. 386)).

Related Fellows

John Flamsteed (1646-1719, British), Astronomer
Jonas Moore (1617-1679, British), Mathematician
Robert Hooke (1635-1703, British), Natural philosopher

Associated place

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