^ ^ ^_ 



2 



MATHEMATICAL and 



their velocities fo accurately adjufted, as not to difFer fen- 

 fibly from the tables of aftronomy in fome thoufands of 

 years. 



For the greater beauty of the inftrument^ the balls rc- 

 prefenting the planets, are to be of a confiderable bignefs; 

 but fo contrived, that they may be taken off at pleafure^ 

 and others, much fmaller, and fitter for fome purpofes, 

 put in their places. 



J- 



When the machine ii 

 a winch, there are three 



point 



of the day, the day of the month and the year, (according 



J 



account) anfwering to that fituation of the 



heavenly bodies which it then reprefented; and fo conti- 

 nually, for a period of 5000 years, either forward or 



backward. 



In order to know the true fituation of a planet, at any 



particular time, the fmall fett of balls are to be put each 



on its refpedlivc axis, then the winch to be turned round 



'till each index points to the given time; then a fmall F^- 



hfcope^ made for the purpofe, is to be applied to the cen- 

 tral ball, and directing it to the planet, its longitude and 



inclination will be feen on a large brafs circle, filvered, 

 and properly graduated, reprefenting the Zodiac-, and 

 having a motion of one degree in 72 years, agreeable to 

 the preceffion of the Equinoxes: So likewife by applying 

 the telefcope to the ball reprefenting the Earthy and di- 

 refting it to any planet, then will both the longitude and 

 and latitude of that planet be pointed out (by an index, 

 and graduated circle) as ktn from the earth. 



Thetwoleffer Faces are four feet in heighth, and 2 feet 

 3 inches in breadth: One of them reprefents and exhibits^ 



.7 



their 



eclipfes, tranfits and inclinations: Likewife all the appear- 

 ances of Saturn^ with his ring and fatellites. And the 

 other reprefents all thephaenomina of the Afoow, particularly 

 the exa£t time, quantity, and duration of her eclipfes, and 

 thofe of the Sun^ occafioned by her interpofition; with a 



moft 



7,^ 



. . I r_ -wj K.y'■;^ti^^^ 



