828 C. A. Young—Displacement of lines in Solar Spectrum. 
Since the points observed were not situated upon the solar 
equator it is necessary to correct each result by multiplying it 
by a factor depending upon the heliographic latitude, ¢, of the 
point. Ifthe sun’s surface rotated as a coherent mass the factor 
would be simply, sec. g. Since this is not the case however, 
the expression becomes more complicated. Adopting Faye’s 
constants and formula of solar rotation, we find the factor, 
1 
t— 
“eos p(1—0°216 sin? p) 
On July 10, p=2°, f=1:001; on July 15, p=8°, f=1°002; 
on Aug. 10, p=14°, f=1:044; on Aug. 12, p=15°, f=1051. 
Appiying the corrections we have the following, in which 
the column headed Us, gives the results without discrimination, 
while the column U’¢ contains the results obtained by throwing 
out the ni-kel line in observations (1), (2) and (6), and rejecting 
entirely (4), while (5) is counted twice, as having double weight 
for the reasons assigned. 
Ue Ue 
(1) 3°55 (1') 3°33 
(2) 3°57 (2) 38°22 
(3) 2°40 (3) 2°40 
(4) 1:16 (4) 2°90 
(5) 2°90 (5) 2°90 
(6) 3°75 (6) 2°99 
(7) 2°80 (7) 2°80 
(8) 2°53 (8) 2°53 
(9) 2-47 (9) 2°47 
Mean 2°79 + 0°18 2°84 + 0°07 
The two results do not differ materially, but the second is 
much more reliable. It makes the velocity of the sun's rota 
Hanover, N. H., Sept. 12, 1876. 
