190

Mechanics.

to be overcome is the Friction of the nu-merous Parts, which are chiefly a Combi-nation of Wheels and Axles, whose Use isto divide a large Portion of Time, as a Dayor Hour^ into very minute equal Parts, asMinutes , Seconds , &c. and to point out thoseDivisions by an equable Motion of a properHand or Index round a graduated Circle(XLII).

In

Ing equably accelerated by the continued Action of theMan) will at the Instant of the Stroke be at the Rate ofeight Yeztper Second ; therefore 8 X 100 st. = 800 Ib.for the Momentum of the Lever or Fly. But since theDiameter of the Screw is but ^ of the Length of theLever, we shall have 30 X 800 Ib. — 24000 Ib. for theMomentum of the Engine, which is equal to that ofIOO Ib. falling 120 Feet; which prodigious Force is stillfarther increased for coining larger Pieces of Money, byincreasing the Weights and Arms of the Fly.

(XLII) 1. I shall here strew the Principles of Watchand Clock-Work, and how to calculate the Numbersfor the Movements, in as clear and compendious a Man-ner as I possibly can. In all Automata , or Machines ofClock-Work, there is a natural Agent or Principle ofMotion ; which, by acting on one Part, gives Motionto that, and all the other Parts depending upon it, andthus becomes the Primum Mobile , or first Mover to thewhole Machine.

2. In common Clocks and Watches this is of two Sorts,viz. A Spring or a Weight ; either of which maybe made to act with any determinate Force ; the Springby its Elajlicity, and the Weight by its Gravity. Inthese Machines this Force is required to be such as willovercome the Vis Inertia and Friction of all the Parts inMotion ; which in Watches is very inconsiderable, butin Clocks is much greater, and that in proportion asthey are more compounded.

3. The