( iVA ) 
\y go back a little, and make a procefHon of the -^qui- 
Haviug thus fettled the true caufes of the Cocleftial MctU 
ons^ he next enquires into the various opinions of Phiiofo- 
phers on that fubjeft, and examines the Phjifica Calefik of 
Kepler^ the Vortices ofC^rte/m^^nd tbofe of the ingenions 
Monfieur Lethnits^ whofe feveral Theories he fufficiently 
confutes 3 and then he gives a^ account of the other three 
celebrated Syftems of the Univcrfe, the Ptolewaick, Tycho^ 
mck, and Semi-Tjchonkk^ and the different forces that are 
neceflary to make the Planeti move in the order, which 
thofe Syftems require. 
In the 2d Book are explained all thofe things that depend 
upon the motion of the PrimumMobile^xht Doftrine of the 
Sphere,theGenefisof the Circles,theufeof theGlobes.Spheres 
and other Inftruments that are contrived to reprcfcnt the 
Diurnal Motions of the Stars, together with the method of 
determining by obfervations the pofitionsof the Circles ia 
refpefl: of each other,and the places of the Stars,their Longi-. 
tudes, Latitudes, c^r. the method ofmakiug Catalogues 
ofthe^xt Stars, with an Hiftorjcal account of all thofe 
Catalogues that have been hitherto made. Here alfo he 
fhows the way ot folving all the common problems of the 
Sphere by Trigonometry^, as alfo the foundation and me« 
thod of making all forts of Dyals by the fame Calculus : And 
laftly the various Ways of determining the Parallax and 
Refraftions of the S ars with their demonftrations. 
In the 3d Book he defcends more particularly to the 
Theory of the Primary Planets. And, becaufe each Planet 
fo moves in an EIHpfe round the Sun, that it defcribes A- 
rea's always proportional to the times, he gives ihe methods 
of dividing ihe Area of an Ellipfe by a Line drawn from 
Its focMs in a given proportion ; which (ray be done either 
by the indired method of Keplau or diredly by a Series of 
his own, which he demon(l:rates^ and then he ftiows Dr 
f^4^r<5/'s Theory ( wherein the Planets are itippofed todefcribe 
about the other /im angles always proportional to the times} 
to 
