222 
MR. IVORY ON THE THEORY 
wherefore, by substituting and dividing all the terms by e sin (v — m). 
edrs— — . %r g . h dh - cos (v — x?)(^i) .r 2 dv. 
dR > 
But hdh — r 2 d v, and, 
, . 1 (dr , dr dv\ 
- cos («>-*) = - 
wherefore, 
, C dv /d R\ /c? ?• , 7' dv\(d R\ I 
ed »=(j- e V^j + t5i + r t »- TeJKTr ) /• 
and, because r 2 dv — 
r~ dv 
a 
^ = av/ ‘~ g -^-^ ( 16 ) 
The variation of g, the longitude of the epoch, must be deduced from the 
equation (9), viz. 
(di-dm) = - p g d-e-da. 
From this d e may be eliminated by means of the equation (7), viz. 
2 
~ ]\ d h — cos (v — m) de e sin ( v — m) dm ; 
and the result will be 
— nr? ;, cos { - v ~' a) (dt-dv) = 
— y'J^hdh — ^ cos (o — ts) — e sin (c — srj ~j~\dw. 
Now the coefficient of d m is equal to 
(1 — e 2 )^ cos (v — txt) — ; 
wherefore, by multiplying by ;- 2 , we get 
a 2 *Jl — e 2 . cos (v — m) (de—dm) = — 2 r . ^ .hdh 
— a { a ( 1 — e 2 ) cos (v — w) — 2 r e} d m : 
