GRAPHIC REDUCTION OF STAR PLACES. 
179 
a horizontal line through B with the line x o already drawn 
gives A' B', which is 
10 i in 
—~sec o = 1.11 
15 
cos a = — 0.368, as before. 
Project B' to B". 
The intersection of a horizontal line through v with the 
line B" o gives the distance A" 
= cos 0 * sec $ — — 0.408. 
15 
The value of C on June 9 is — 3.57. 
The intersection of a vertical line through the extremity 
of A" with the line V"o determines the line p, which is 
equal to 4- 0.15. 
Hence P = ^?cosa sec d X C — + 0.15. 
As in the case of b B, the true value of the last result is 
given by multiplying finally by 0.357 instead of 3.57; this 
corrects for the artifice employed of magnifying the first 
partial result, viz., ~ sec S, in order to secure one more deci¬ 
mal place. In the case of c C, since both cos a and sec d are 
vertical lines, the latter is multiplied by in order to 
change its direction and thus facilitate its multiplication by 
cos «. 
Fourth term .—To find d D = sin a sec 8 X D (see plate 9). 
15 
As in the previous case, we have ^ sec d = A' B' = 1.11, 
and by previous construction sin a~ a b~ — 0.930 X 20. 
25—Bull. Phil. Soc., Wash., Vol. 13. 
