[ 413 ] 
V 
A b uu d t x -, fince thefe arcs, which meafure equal 
angles, are as their radii g and r. 
We {hall have, therefore, in the above c . Troblem , 
r du d t , A , r , 
— — , = 2 7T r x ~ A b u u 'A - d t > 
V aa — uu P g 
Ss 7 or 
rr 
whence we get dt ■ 
T d u 
2vVaa-uu 1+Abuu ^ 
•r " 
rr 
But- 
14* A b u u x 
T 
■= 1 — Abuux 
r 
2 TTg 
iTTg 
■4 
2 TT g 
where the other terms may be neglected which con- 
tain the powers of A , becaufe A is a very fmall fra- 
ction. 
We {hall have, therefore, d t = — — — x 
V aa — uu 
rr 
T \ 
(1 — A buu x )• and the inftantaneous pre- 
lirgJ 
ceflion will be ^ £ x — x — — 11 x { 1 — Ab uux 
2 t V aa — uu 
rr 
*r\ 
/ whofe integral for the fir ft term, in the folfti- 
2jrg^ 
cial point, where u — is A b x — x , as was 
r iir 4 rr 
feen in the preceding Problem . But the integral of 
^ u 
