Bennett—Actinometric Observations of the Solar Eclipse. 371 
where Q) and & can be determined by two observations; and they 
can be so determined that Q = ; where y is the ordinate of a point 
on the required curve. 
Thus if 
Q: & Qoe7* COED, 
and Gh = Gig? Cee, 
log Cs \ 
then ip = »/ ie (3) 
9 
COSEC dz — COSECC ay 
and substituting this value of & in either of the above given equa- 
tions, we find Q. 
Again the altitude of the Sun is given 
in terms of the hour angle (h) by the 
formula 
sin a = sin g sin 6 + cos p cos 6 cosh, (4) 
where 
@ = latitude of Dublin = 53° 2387, 
and 
© = declination of Sun on May 28th 
= 21° 265 approx. 
Thus at the beginning of the eclipse 
h = (2" 18”) x 15 = 88° 15, 
and wa = 48° 40’. 
Again for the time Any37 = — 692 Lo, 
and % Gh S 2 IS 
Thus 
(st = Qe Reosecsso15" for the point A, 
ae = Quen ore tor a point near C- 
Hence 
133 = Too cosec@ : 
282 Bao) (5) 
Y 
2) 
eae | 
= au 2 
This then is the equation of the theoretical curve. 
