PreceJJion of the Equinoxes. 367 
•of the diameters as 229 : 230 ; but if the greatefl nuta- 
tion of the earth’s axis be rightly ascertained, the preceflion 
is only about 14 ; which difference between the theory 
and what is deduced from obfervation muft arife either 
from the fluidity of the earth’s furface, an increafe of den- 
sity towards the center, or .the ratio cf the diameters being 
different from what is here aflumed, or probably from all the 
caufes conjointly. But as the heft obfervations muft be liable 
to fome fmall degree of inaccuracy, and an error of one 
or two feconds in the nutation will, in this cafe, make a very 
confiderabie alteration in the concluflon, the eflimation of the 
preceffion arifing from the adtion of the fun feems to be fubjedt 
to a very conflderable degree of uncertainty. 
G gg 
Vol. LXXVII. 
