TRANSACTIONS 



OF THE 



American Philosophical Society, &c. 



SECT. I. 



-"* 



Mathematical am^ Astronomical Papers. 



... 



L 



A defcription of a new Orrery, planned and notv near^ 

 ly fnijhed by David Rittenhouse, A.M. of Nor- 



ritony in the county of Philadelphia. Communicated by 



'■ jDr. Smith. 



Read aift 

 Mar. 1768. 



■ f 



HIS machine is intended to have threej^^^x, 

 Handing perpendicular to the horizon: 

 That in the front to be four feet fquare, 

 made of fheet brafs, curioufly polifhed, filvered and paint-' 

 ed in proper places, and otherwife ornamented. From 

 the center arifes an axis, to fupport a gilded brafs ball, in- 



the /Z 



Round this ball move others. 



made of brafs or ivory, to reprefent the planets x They are 

 to move in elliptical orbits, having the central ball in one 

 focus; and their motions to be fomctimes fwifter, and 

 fometimes flower, as nearly according to the true law of 

 an equable defcription of areas as is pofTible, without too 

 great a complication of wheel-work. The orbit of each 

 planet is likewife to be properly inclined to thofe of the 

 others; and their Jphelia and Nodes juftly placed; and 



Vol, I. 



A 



their 



