-66 Mr. Vince on the 
for the fine and cofine of the fun’s declination, the ratio of the 
velocities in "the laft article becomes . I# 
y. Hence if TSL (fig. 2.) be the ecliptic to the radius 
unity, P the plane of the fun, SER the equator, PE the fun’s 
declination, and we take Ec : cd ( cd being perpendicular to 
Ec) :: 1 : 3 — , and through J, E, defcribe the great circle 
TEM, then will ST be the preceffion of the equinox during the 
time the fun defcribes y in the ecliptic. Now E d (or Ec, as 
the angle at E is indefinitely fmall) : dc :: rad. =1 : fine 
angle E== - f— hence (if SV be drawn perpendicular to 
TE) 1 : fine SE :: *1^1 : S y^3^x fm. se xj . therefbre> 
fm. STV or ESP : i :: SV : 
P x fin. ESP 
8. Now — fin. SP, and hence -r 
fin. ESP cof. ES iin. ESP 
vw 
fin. SP x cof. SP 
cof. ES 
; but 
cof. ESP 
tan. ES X cot. SP 
= i, hence 
vw 
fin. ESP 
fin. SP x cof. SP X cof. ESP fin. SP 2 x cof. ESP r , 
r VQ - ■ , — -55- = ? — — ; confequently, 
cof. ES x tan. ES x cot.SP fin. ES - 1 J 
g T _ 3 *pr X fin. SP* X cof. ESP X i- _ * _ fm> gp) 
3^.-Xc° _ f. ESPX^ w hofe fluent, when * = i, is w>rxcof - ESPxy 
(y being now = to a quadrant) the arc of preceffion whilft the 
fun defcribes 90° of the ecliptic ; and to find the degrees fay, 
.. 3 at>r x c °f ESP.x y , 0 ^afir x cof. ESP r . 
4y : 3 6 ° :: yy : 3 60 x > confequently 
the preceffion in a year — 360° x — ■ tL nf, - ES -- = 2 i // 6 W . This 
would be the preceffion of the equinox arifing from the attraction 
of the fun, if the earth were of an uniform denfity, and the ratio 
of 
