[ 8*o ] 
lphere might produce in the motion of a fatellite re- 
volving about it, and as it is the cafe of the bodies 
of the Earth and Jupiter which have Satellites about 
them, not to be Spherical but fpheroidical, I thought 
it worth while to enter upon the examination of fuch 
a problem. When the primary planet is an exaCt 
globe, it is well known that the force by which the 
revolving fatellite is retained in its orbit, tends to the 
center of the planet, and varies in the inverfe ratio of 
the fquare of the didance from it; but when the pri- 
mary planet is of a fpheroidical figure, the fame 
rule then no longer holds: the gravity of the fatellite 
is no more directed to the center of the planet, nor 
does it vary in the proportion above-mentioned ; and 
if the plane of the Satellite's orbit be not the fame 
with the plane of the planet's equator, the protuber- 
ant matter about the equator will by a condant effort 
of its attraction endeavour to make the two planes 
coincide. Hence the regularity of the Satellite's mo- 
tion is neceflarily diflurbed, and though upon ex- 
amination this effeCt is found to be but Small in the 
moon, the figure of the earth differing fo little from 
that of a Sphere, yet in Some cafes it may be thought 
worth notice ; if not, it will be at lead a Satisfaction 
to fee that what is negleCted can be of no confe- 
quence. But however inconfiderable the change may 
be with regard to the moon, it becomes very fenfible 
in the motions of the Satellites of Jupiter both on ac- 
count of their nearer didances to that planet when 
compared with its femidiameter, as alfo becaufe the 
figure of Jupiter fo far recedes from that of a Sphere. 
This I have Hiewn and exemplified in the fourth la- 
tellitc : in which cafe indeed the computation is more 
exaCt 
