PENDANT PLANETARIUM. 85 



glafs globes filled with mercury. The fun may be a 

 globular glafs fountain-lamp with a cork fitted to the 

 tube, containing a tin pipe for the wick, fo that the 

 blaze being in the centre of the globe and furrounded 

 with oil, will be magnified on every fide and exhibit a 

 fplendid fun. It will be readily underftood that mo- 

 tion is to be given to the wheels, turning the cannons, 

 &c. by an arbor having as many wheels as the pla- 

 nets have, all firmly fixed to the arbor and calculated 

 to move them in their proper periods. The whole 

 may be made of wood, if required, and the wheels 

 turned by elaftic wire bands. To the machinery may be 

 attached a fimple movement whofe weight may defcend 

 down the wainfcot of the room in any convenient place. 

 Thus the planets will be feen moving round the fun in 

 the concave above, in elliptic orbits and inclined 

 planes, apparently revolving in the heavens without any 

 fupport. 



It is eafy to conceive how the fame principle, as far 

 as it refpedVs the excentricity and angles of inclination, 

 may be applied to either vertical or horizontal orre- 

 ries ; by having the wires which fupport the planets fuf- 

 ficiently ftout to bear their weight either in a perpendi- 

 cular or horizontal pofition, and fliding in and out of 

 fmall tubes as they pafs round in the elliptic grooves on 

 the face of the orrery. They may be drawn in by 

 the wheel pin and cord as defcribed in fig. 2. and forced 

 out by fmall Iprings, In this cafe their latitude may be 

 marked on the fupporting wire, and the top of the tube 

 in v;hich they Aide will ferve as an index. Or the degrees 

 may be marked on the edge of a groove cut in the tube 

 through which an index, faftened to the moving wire 

 or rtem which fupports the planets, may pais ; and thus 

 give the latitude. 



BURGISS ALLISON. 



Vol. v. M No. 



