Parallax of the Plxcd Stars. toy 
we are to expert to fee be ~~~ l P ; or ^ths of the total paral- 
lax of a fixed har of the firlt magnitude ; and if we fhould, 
by obfervation, find the partial parallax between two fuch 
hars to amount to i /7 , we fhall have the total parallax P = 
I X I X I 2 4 , 
— — — i^jOpop. If the hars are of the third and twenty- 
^ m * .24 2 2 1 
fourth magnitude, the partial parallax will be — — — P ; and 
if, by obfervation, p is found to be a tenth of a fecond, the 
i x ^ x 24 
whole parallax will come out : j o ■ = o', 3428. 
It will be necelfary to examine fome different fituations. 
Suppofe the hars, being hill in the ecliptic, to appear in one 
line, when the earth is in any other part of its orbit between 
O and E ; then will the parallax hill be exprefled by the fame 
algebraic form, and one of the maxima will hill lie at O, the 
other at E ; but the whole efteft will be divided into two parts, 
which will be in proportion to each other as radius — fine to 
radius -p fine of the liars diftance from the neareh conjunction 
or oppofition. 
When the liars are any where out of the ecliptic fituated fo 
as to appear in one line Oabc at rectangles to OE, the maxi- 
771 **** M 
mum of parallax will hill be expreffed by P ; but there 
will arife another additional parallax in the conjuCtion and op- 
pofition, which will be to that which is found 90° before or 
after the fun, as the fine (S) of the latitude of the hars feen at 
O is to radius (R) ; and the effect of this parallax will be di- 
vided into two parts ; half of it lying on one fide of the large 
har, the other half on the other fide of it. This latter paral- 
lax, moreover, will be compounded with the former, fo that 
P 2 the 
