IN PHYSICAL ASTRONOMY. 
275 
d 3 . r* 
2d t* 
d- . r 3 S . — 3d 2 .P 
r +- 
d t J - 
2 d t- 
-R + JL + iJiR + r^U^ =0 
d 2 z p z m ( z _ 3 m, z r r cos — X) _ g 
d £ 3 r 3 r ( 3 r, 5 
=^-^) d - 'i;r {/or 
d i? = the differential of R, supposing n t only variable + the differential of R, 
with regard to n l t only in as much as it is contained in the terms in 
r, X and s due to the perturbations ; hence 
d R = the differential of R, supposing only n t variable + ^ . d . I r -j- ~ d . § 
d R 
+ d r d .Is; d . § r', d . £ >1, and d . %s, being restrained to mean the 
differentials of those quantities with regard to n l t only. 
■ * = ($ * -*+ (h s ) - m *— * q •" w + q + q * 
( t being used in the sense n t — n l t .) (717) Ss = 2V 3 sSs near ^y- 
(^) d ^+Q d - ,A 'H^) d - Js= ^^ 
d.r d . Sx' and d . Is being restrained to mean the differentials of 
those quantities with regard to njt only. 
\dx'J 
Z S$ 
