I 811 ] 
^exad than it would be for the other fateilites : for as 
my firft defign was to examine only how far the 
moon’s motion could be affeded by this caufe, I fup- 
pofed the fatellite to revolve at a distance fomewhat 
4 emote from the primary planet, and the difference 
of the equatoreal diameter and the axis of the planet 
not to be very confiderable. There likewife arifes 
this other advantage from the prefent theory, that it 
furnifhes means to fettle more accurately the propor- 
tion of the different forces which difturbthe celcftial 
motions, by affigning the particular fhare of influ- 
ence which is to be afcribed to the figure of the cen- 
tral bodies round which thofe motions are performed. 
I have added at the end a proportion concerning 
the diurnal motion of the earth. This motion has 
been generally efteemed to be exadly uniform } but 
as there is a caufe that muff neceffarily fomewhat al- 
ter it, I was glad to examine what that alteration 
could amount to. If we firft fuppofe the globe of 
the earth to be exa&ly fpherical, revolving about its 
axis in a given time, and afterwards conceive that by 
the force of the fun or moon railing the waters its 
figure be changed into that of a fpheroid, then accor- 
ding as the axis of revolution becomes a different di- 
ameter of the fpheroid, the velocity of the revolution 
muft increafe or diminifh : for, fince fome parts of the 
terraqueous globe are removed from the axis of revo- 
lution and others depreffed towards it, and that in a 
different proportion as the fun or moon approaches to 
or recedes from the equator, when the whole quan- 
tity of motion which always remains the fame is dif- 
tributed through the fpheroid, the velocity of the di- 
urnal rotation cannot be conftantly the fame. This 
5 L 2 variation 
