Explanations of time-keepers, constructed by Mr. Thomas Earnshaw and the late Mr. John Arnold / Published by order of the Commissioners of Longitude.

  • Earnshaw, Thomas, 1749-1829.
Date:
1806
Catalogue details

Licence: Public Domain Mark

Credit: Explanations of time-keepers, constructed by Mr. Thomas Earnshaw and the late Mr. John Arnold / Published by order of the Commissioners of Longitude. Source: Wellcome Collection.

    18/86 (page 10)
    their nature, which lias been suppos’d ; for when it is certain that all causes of error may be over compensated, we cannot despair of finding the Medium, and which may he easily prov’d by examining the going of my Timekeepers. It will there appear that what errors, they are subject to, arise from causes certain and natural, and in course may be corrected bv art. The Detach'd Escapement is a Dead Scape, if properly unlock’d as I have done it, on the outside of the wheel. The unlocking on the in- side is improper, being against the whole train of Wheels and causes a recoil. When the wheel is lock’d on the heel of the tooth instead of the extremity ; the absurdity of this is too plain to the meanest Me- chanick to need any comment; the notches cut by the pallet rubbing on the round face of the Scape Wheel teeth clearly prove how much friction presides there; and such a wheel is much more difficult to make than mine. My size of pallet evidently tends most effectually to prevent watches stopping. 1 With respect to the preferrence to be given to box above pocket- Timekeepers, I think the former are the best for the following reasons. Every Watchmaker surely knows the Influence of oil. Therefore if oil by its change robs a main Spring of the force of one pound of its. power, then a Main Spring of the force of one Ounce must be Sixteen times more affected by it. This is Avell known by the effect produced by the change of oil on pivot detents, when Time-keepers are made of a large size, merely for the purpose of having a Large and Powerful Main Spring to drag the Works on through all Impediments of oil and. dirt; but before this is done it should be considered whether a greater evil is not likely to happen, namely, the Evil of Friction, far greater than that of oil. There is a Happy medium between these two. Evils. Whether I have found out that Happy Medium or not, I leave to the Examination of every Impartial man who may Examine my Timekeepers, in which, he will not find cuttings and tearings in any part or hardly be able to discover in the oldest of them the least trace ^ or place mark’d on which the Escapement has acted. Thus then mjr