( 8; ) 



No. XII. 



A Def crip don of the Fendant Flanetarium. By BuR- 

 Giss Allison. 



Read May sd, 1800. 



a a a a is a frame fupporting the whole machine. 

 3 ^ is a iixed rod or arbor fupporting the fegment c, 

 and the fun j- by a fine wire, rf' is a wheel fixed to the 

 upper part of the cannon e carrying round by its lower 

 end the arm ff and the planet Mercury fufpended by a 

 fine dark wire. ^ _^ is an arm fixed by fcrews into the 

 frame a a Sit each end, and alfo to the upper end of the 

 fixed cannon /j b, which fupports by its lower end the 

 frame//, which, as explained in fig. 2. is an elliptic 

 plane, fupporting by four or more ftuds / / the concave 

 piece k k forming an elliptic rmg. m r,i is a wheel on 

 the moveable cannon n n which carries the arm 

 fupporting on one end the planet Venus by a fine wire, 

 as above, p p s.?, before is a fixed frame attached to the 

 immoveable cannon q and the elliptic plane r r, fup- 

 porting by finds the concave ring j- j-, ut fupra ; and 

 thus the wires by which the planets are fufpended, and 

 the concave rings are alternately fupported by ihe move- 

 able and fixed cannons, &c. until the whole forms a 

 concave like the heavens ; having the fmall grooves or 

 apertures through which the planets fupporters move 

 round, forming elliptic lines in the concave fegment of a 

 fphere marking out the planets paths, according to their 

 excentricity and fhevving at one view the places of aphe- 

 lion, perihelion, &c. of all the planets. The concave 

 fegment being painted a dark blue and fpangled with 

 filver ftars in the pofition that fome of the fixed ftars 

 would appear from the centre of the fun, will have a 



fine 



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