[ 3 6 3 ] 
XXXVI, On the PreceJJion of the 'Equinoxes . By the Rev. 
Samuel Vince, M. A. F. R. S. 
Read June 21, 1787. 
1. F | 1HE true caufe of the preceflion of the equinoctial 
JL points was firft affigned by Sir Isaac Newton ; but 
it is confefled, that he has fallen into an error in his inveftiga- 
tion of the effeCt. Without, however, entering into any enquiry 
relative to the circumftances in which he has erred, I propofe to 
fhew how we may obtain a true folution from his own principles, 
by means of which alone the whole calculation may be rendered 
extremely limple and evident : and although very fatisfaCtory 
folutions have been already given, yet the importance of the 
problem will fufficiently apologife for offering any thing fur- 
ther upon the fubjeCt that may at all tend to elucidate it, 
2. Let S (Tab. XV. fig. 1 .) be the fun, ABDC the earth, T its 
center, EQ^ the equator, P ,/, the poles ; draw CTB perpendi- 
cular to SAD, and join SE, which produce to meet CB in K. 
Call the radius ET unity, and let the force of the fun on a 
particle at T be then the force on a particle at E = 
— * hence, if we refolve this latter force into two others, one 
se 2 * 9 
in the direction ET, and the other in the direction parallel to 
TS, we have SE : ST :: ; the force in the direction parallel 
to 
