240 Mathematical Elements Book IV. ]

239 the Law of Gravity* ; so that if we add to these* 12oS * what we have said ot the Deflection of Saturn ,I270 nothing will remain to be explain’d in respectthe primary Planets.

1276 That the Motion of Comets depends upon the

of Gravity, is also deduc’d from Observations,and in respect of them, as has been said concern"ing the Planets, the Sun’s Gravity prevails, a11by that Gravity they deflect from a rectili neaI ”

* 980 Course* ; but that the Curvature of their

226 depends upon. the same Gravity, follows si -0 ” 1this; that a Body, by that Gravity, will d e 'scribe an Ellipse, or a Parabola, or an HyP er '

* 241 bola * ; which Lines it appears that those Coso“ tS1208 have described, whose Trajectories have been^

termined. {

1277 Phe Satellites of Jupiter and Saturn are

* 944 by the fame Laws about their Primaries, as the P f

marks are moved about the Sun* ; wherefore r*1275 Explication of those Motions * may be also

ferr’d to them ; for in these three Cases, so 13 e £Bodies are revolving at different Distances a hora much greater Body; namely, Satellites abo uJupiter and Saturn, and primary Planets abothe Sun.

1278 Whilst secondary Planets are moved about a r ,mary one , it is evident that they may all be ,n s ewith one common Motion, whereby the respec ‘ -Motions with which they are mov’d in respeceach other, will not be disturb’d, because a Bo /

. may at the same time be mov’d by different

* 125 preffions*; the Motion that a primary P^! 1

has in common with its Satellites, is the M° nof a primary Planet about the Sun.

Yet the Motion of the secondary Planets is disttifby the Action of the Sun, towards which they are &tied, sometimes faster, sometimes flower, acc° r ^ing to the different Position of the Primary;

12 79