[ 422 ] 
a a 
being by Art. 17. = B b x — x^> and by Prob . 
2 r 
VIII. the fpaee run through parallel to the plane of 
the ecliptic, will b sBbx — xdtx = (by the 
P X 
zrr 
preceding denominations) Bb x— x — x 
d z 
f. 
a**~* * * nT 
x — B x — x — x 
a c 
r 
r 4^ Vxx, ££ 
2rr 27 r V XK -a5 
and putting inflead of-, its value, which was found 
be ^ 7 we fhall have B x f 
d z 
to 
a c 
xg — «x 
V XX — 
X — x Jj+gx 
4 t cc 6 
V 
j and when the point 1 ° is on 
the other fide with regard to l\ we fhall have B x — 
/ ~ — r — dz 
X ^ x £ + * x 77= 
wu V xx. 
nf 
4 vr 
Therefore 
always taking the precefiion for the two points to- 
gether placed on either fide of l\ and at an equal di- 
itance from it, we fhall have, by joining the two values 
• now found, after making reduction, B x — x J— x 
4 7T 
^ « „ nT fg 
■—=.======, or Z5 x — x x 
V xx — ,22; 2 7 r a a 
IgJJ— *S ZZ * 
//— 
X 
d z 
V*: 
Put 
