378 CAPTAIN W. DE W. ABNEY AND DR. T. E. THORPE ON PHOTOMETRIC 
sky. Hence the readings on the bar photometer are necessarily higher than those 
obtained by the integrating box. 
Table IV.—Headings on the Integrating Box reduced to Values of Light Intensity. 
Voltameter readings. 
Value of light at 1 foot 
from screen in Siemens 
units. 
Approximate time when 
readings were made from 
beginning of totality. 
5-4 
•0197 
15 
! 6-2 
•0122 
30 1 
5-9 
•0142 
45 ! 
7-0 
•007,5 
60 , 
6-8 
•0085 
75 ! 
71 
•0070 
90 j 
7-3 
•0065 
105 I 
7-3 
•0065 
120 
7-7 
•0054 
135 1 
7-8 
•0051 
150 
8-3 
•0045 
165 
8-8 
•0040 
180 
8-9 
•00.35 
195 
9-3 
•0030 
210 
9-4 
•0027 
215 
9-4 
•0027 
220 
Table V.—Readings on the Bar Photometer reduced to Values of Light Intensity. 
Value of the lamp = 0T33 unit. 
Distance of lamp from 
screen in inches. 
Equivalent value in 
Siemens unit at 1 foot. 
Approximate time of 
reading. 
1 33-5 
•0160 
50 
i 34-4 
•01.52 
70 
1 36-2 
•0137 
90 
, 39-1 
•0118 
110 
! 39-6 
•0115 
130 
I 44-1 
•0093 
150 
46^4 
•0084 
170 
47-8 
•0079 
190 
48'0 
•0078 
210 
47-8 
•0079 
2-20 
48-5 
•0077 
230 
It will be noticed that Lieutenant Bairnspather’s first reading was made when 
50 seconds of the totality had passed. The delay was due to the circumstance that 
it was found necessary to diminish the number of cells connected up after totality had 
begun, and hence a new reading of the galvanometer was needed before the observa¬ 
tions could be commenced. The actual time of beginning could only be very approxi- 
