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The Principles of Mr. Harrison's Time-Keeper
keeperSat 9 November 2024 Tagged: clocks This post is a transcription, plus some commentary, of the Board of Longitude's 1767 document "The Principles of Mr. Harrison's Time-keeper", from scans on the University of Cambridge Digital Library.
Sat 9 November 2024Tagged: clocks This post is a transcription, plus some commentary, of the Board of Longitude's 1767 document "The Principles of Mr. Harrison's Time-keeper", from scans on the University of Cambridge Digital Library. In this post I have updated spelling to match modern usage, and turned Roman numerals into normal digits, but left sentence structure and capitalisation the same. As soon as the watch is put together, Mr. Harrison says, it will show its rate of going in three hours accurately the same which it will keep afterwards; so that he can soon determine it by comparison with his pendulum clock.The balance-spring, when at rest, touches the cycloid-pin; and does not begin to leave it, until the balance has vibrated an arc of forty five degrees beyong the point of rest, while the spring is in the state of coiling itself up.The thermometer curb is composed of two thin plates of brass and steel riveted together in several places, which, by the greater expansion of brass than steel by heat, and contraction by cold, becomes convex on the brass side in hot weather, and convex on the steel side in cold weather; whence, one end being fixed, the other end obtains a motion corresponding with the changes of heat and cold, and the two pins at this end, between whcih the balance-spring passes, and which it touches alternately as the spring bends and unbends itself, will shorten or lengthen the spring, as the changes of heat and cold would otherwise require to be done by the hand, in the manner used for regulating a common watch.Mr.
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