168 
PRESTON. 
of the arcs. The negative sign before 16 indicates that the 
cosine of the right ascension is minus. This quantity, which 
is — 7.38, is to be multiplied by the value of A on June 9. 
On this date we see, by inspection of plate 7, that A equals 
+ 0.507 X 10 or the line HI. In order to multiply the two 
lines F G and H I, I is projected to J. The point J is the 
intersection of a horizontal line through I and a vertical line 
at a distance of 10 units from the origin 0. The point of 
intersection of the vertical through G and the line J 0 de¬ 
termines the length of the line KL, which is equal to F G 
multiplied by HI, or 20.05 cos a X i; therefore a' A = 
Star No. 1381.— Catalogue of Stars for Observations of Latitude. 
(Report of U. S. Coast and Geodetic Survey for 1876, Appendix No. 7.) 
Reduction from mean to apparent declination. 
Log. No. 
a= 16 h 33 m 41 s = 248° 25' sin a = 9.9684n — 0.930 
d = 53° V cos a = 9.5657n — 0.368 
sin d = 9.9030 +0.800 
cos d — 9.7783 +0.600 
Terms 
a / 
20,052 cos a 
b' 
— sin a 
c' 
tan uj cos d 
— sin a sin d 
d' 
cos a sin d 
Logs 
Logs 
Logs Logs 
Logs 
Computation. 
1.3022 
9.5657n 
9.6373 9.9684n 
9.7783 9.9030 
9.5657n 
9.9030 
Log a / V c/ d / . 
0.8679n 
9.9684 
9.4156 9.8714n 
0.2604 0.7437 
+ 1.004 
0.0017 
9.4687n 
“ A B C D . 
9.7055 
0.9215n 
0.5521n 
1.3026n 
0.5734n 
0.8899n 
0.5538n 
0.7713 
Nos ..a'A,b'B, c'C,d'L>. 
— 3.74 
— 7.76 
— 3.58 
+ 5.91 
For June 9: 
Nos. a' b' c' d' .... 
— 7.38 
+ 0.930 
+ 1.004 
— 0.294 
“ ABC D . 
+ 0.508 
— 8.35 
— 3.57 
—20.07 
