C 3 °9 ] 
time of defcent from any point p will be 
= -T~i — ^ X E -b 2AE — pn — ps. 
X 2a — d 
The femi-tranfverfe AC (fig. i.) being ■=z.ns% 
the femi-tranfverfe eg (fig. 2 .) z=.np\ 
and the femi-eonjugate in each figure :=: ps. 
Since writing the above, I have difeovered a ge- 
neral theorem for the rectification of the Hyperbola, 
by means of two Ellipfes j the inveftigation whereof 
I purpofe to make the fubjeCt of another Paper. 
XXXVII. Jl 
