[ 395 ] 
which becomes = © when the point g can be taken =■ 
y, as may be done throughout the whole extent of the 
circle PEP'E'P-, but if the zone EP' E' PEF'E FE 
be taken away from this circle, to have the true figure 
of the earth, we (hall have g — gf x gr y and y — 
— yf * y £> taking the points g and y for the ele- 
ments of the zone, and g — y = gf x y g — g r, 
becaufe >/ = gf 
Let the lines C S and C P, or C E> be called s and 
<7, refpeftively ; the radius i, or unity ; the fine of the 
angle S C P, V-, its cofine, or the fine of the angle 
S CE , u i C K, x ; g K, y, g m, z y_M, z ' ; gf 
or yf, d u ; P Fy a a ; we fhall have g n — a z-, y v 
— a z (by the property of the ellipfe) ; alfo calling 
g r, r ; and y £, g ; and regarding the little triangle 
g r n as a right-lined one, and fimilar to the triangle 
z 
g Cm y we fhall have r — — x a z, and likewife g = 
z' , 
— x a z . 
a 
By the proportion of fines to the fides of triangles, 
we fhall have y G = y V: C N — x u. Finally, if 
we confider the point S , or the fun, as at an infinite 
diftance, we fhall have Sg = SK=SC — C K = 
s — x, and S g' = S K — S C -f C A' = s -j- x. 
j 3 -f- 3-r* -f $sx + x ' 
Therefore =- 
D d d 2 
*>g 
