[ 420 ] 
fpheroid, let AE#F (Fig. 2 .) be the equator, and 
P p the axis of the fpheroid : alfo let H E C F repre- 
fent the plane of the ecliptic, S the place of the fun, 
and HAPNH the plane of the fun’s declination, 
making right-angles with the plane of the equator 
AEtfF: then, if AK be fuppofed parallel, and 
OKM perpendicular, to O S, and there be affumed 
and t to exprefs the refpeCtive times of the annual 
and diurnal revolutions of the earth, it will appear 
(from the Principia , B. III. prop, xxv.) that the 
force, with which a particle of matter at A tends 
to recede from the line O M in confequence of the 
fun’s attraction, will be expreffed by|4yX^-^X f ; 
f denoting the centrifugal force of the fame particle, 
arifing from the diurnal rotation. Hence, by the 
refolution of forces, X X 2^ X f will be the 
effedt of that particle, in a direction perpendicular to 
O A, to turn the earth about its center O. 
Fig. 2 . 
But 
