( 443 ) 
great Difcoverles ftould have efcaped tKe acute Dif- 
quifuions of the beft Philofophical Heads of all paft 
i^ges, and be referved to thefe our Times. But that 
wonder will foon ceaft, if it be confidered how great 
Improvements Geometry has received in our Memory, 
and particularly from the profound Difcoverits of our 
incomparable Author. 
The Theory of the Motion of the primary Flanets 
is here Shewn to be nothing elfe, but the contemplation 
of the Curve Lines which Bodies caft with a given Ve- 
locity , in a given Direction, and at the fame time 
drawn towards the Sun by its gravitating Power, would 
defcribe. Or, which is all one, that the Orbs of the 
Planets are fuch Curve Lines as a Shot from a Gun de- 
fcribesin the Air, being caft according to the diredlion 
of the Piece, but bent into a crooked Line by the fu- 
pervening Tendency towards the Earths Centre: And 
the Planets being fuppofed to be projeded with a given 
Force, and attraAed towards the Sun, after the afore- 
faid manner, are here proved to defcribe fuch Figures, 
as anfwer punctually to all that the Induftry ©t this 
and the laft Age has obferved in the Planetary Motions, 
So that it appears, that there is no need of folid Orbs 
and Intelligences, as the Ancients imagined,* nor yet of 
F^rtkes ot Whirlpools of the Celeftial Matter, as Des 
fuppofes; but the whole Affair is fimply and 
mechanically performed, upon the (ble Suppofuion of 
a Gravitation towards theSun ; which cannot be denied, 
, The Motion of Comets is here (hewn to be compound^ 
ed of the fame Elements, and not to differ from Pla- 
nets, but in their greater fmftneft, whereby overpow- 
ering the Gravity that fhould hold them to the Sun, as 
it doth the Planets, they flie off again, and diftance 
themfelves from tht Sun and Earth, fo that they fooa 
are out of our fi^t. Aoitiie imperfeft Accounts and^ 
