199

Mechanics,

in the Box G. During this Motion the pinsi?, e, e yof the Pin-Wheel I, take the Tail of the Hammer T,and carrying it upwards remove the Head of the Ham-ster s from the Bell R ; then being let go by the Pin itis made by a strong Spring to give a forcible Strokeupon the Bell, and this is repeated as often as the Hourrequires, by Means of a Contrivance in another Part.

36. This consists of moveable Wheels, and severalLevers, and other Parts, which cannot be understoodby a bare Description, or even by a Representation ina Draught, so well as any Per son may have an Idea ofthem by taking oft' the Face or Dial-Platc of a late-made Eight-Day Clock ; for, within 8 or 10 Yearspast, great Improvements have been made in this Partof the Mechanism. Of which, perhaps, I may give amore ample Account in another Place, the Scope ofmy present Design not admitting it here.

37. To the Invention of Mr. Maurice TVheeler weowe the curious Contrivance of a Clack descending on anInclined Plane ; the Theory of which is worth any Gen-tleman’s Knowledge, and may be seen inN° 161. of thePhilosophical Transaftions . Also the Clock itself maybe seen at Don Saltero’s Coffee-house in Chelsea.

38. But since many People may have a Curiosity tobe acquainted with this odd Kind of Machinery, whohave neither of the Opportunities abovementioned, Iwill here present them with a short Account of thisClock. DE is the inclined Plane on which the ClockABC descends ; it consists externally of a Hoop, andtwo Sides or Plates standing out beyond the Hoopabout a- of an Inch all round, and indented that theClock may not side, but turn round as it moves down.

39. One of these Plates is inscribed with the 24Hours, which pass successively under the Index, whicqis always in a Position perpendicular to the Horizon,and shows the Hoar on the Top of ihe Machine: Forthis Reason the lower Part of the Index is heaviest,that it may preponderate the other, and always keepit upright as the Movement goes on.

40. For the internal Part or Mechanism, let LEDQ_£c the external Circumference of the Hoop, and ff the

O 4 Frarne-

Plate X rFig. 7.