iq6

Mechanics.

low’d 40, or 48, or 56 Teeth, it must drive a Pinioiiof 5, 6, or 7 Leaves on the Balance-Wheel.

25. By this Means all the Wheels and Pinions aredetermined, and adjusted in the Body of the Watchfrom the Fusee to the Balance; but all that v/e havehitherto done shews only the Minutes of an Hour, andSeconds, or Quarter Seconds of a Minute ; but nothinghas yet been mention’d relating to the Mechanism forshewing the Hour of the Day, of which we shall treatin the next Place.

PlateXI. 26. This Part of the Work lies conccal’d from Sight

Pin-. 2. between the upper Plate of the Wateh-Frame and theDial-Plate ; and since few People have the Opportunityof viewing this Worky I have here represented it by aFigure; wherein ABC is the uppermost Side of theFrame-Plate, as it appears when detached from theDial-Plate ; the Middle of this Plate is perforated witha Hole receiving that End of the Arbor of the Centre-Wheel which carries the Minute-Hand ; on this End ofthe Arbor, near the Plate, is six’d a Pinion ah of 10 Teeth ;this is call’d the Pinion df Report-, it drives a Wheeled of 40 Teeth ; this Wheel cd carries a Pinion cf ofi 2 Teeth, and this drives a Wheel gh with 36 Teeth.

27. As in the Body of the Watch the Wheels everywhere drive the Pinions, and so quicken or increase theMotion; here, on the contrary, the Pinions drive theWheels, and by that Means decrease the Motion, whichis here necessary ; for the Hour-Hand, which is carriedby a Socket fix’d on the Wheels, is required to movebut once round, while the Pinion ah moves 12 Timesround. To this End the Motion of the Wheel cd is +-of the Pinion ah, because 10)40^ —4. Again, whil ethe Wheel cd, or the Pinion ef, goes once round, i?turns the Wheel gh but ‘ Part round, for 1 ?.)g6( — 3.Consequently the Motion of gh is but f of * of theMotion ah ; but ^ of ' — that is, the Hour-Wheelgh moves once round in the Time that the Pinion ofReport on the Arbor of the Centre or Minute-Wheel'ma ices twelve Revolutions, as requir'd.

28. Having thus shewn the Nature and Manner oftire MsJunism os a Watch, the Structure of that Part

of