INTENSITY OF CORONAL LIGHT DURING THE SOLAR ECLIPSE OF 1886. 375 
In all, 15 comparisons were made out of the 16 originally intended. At about 
GO seconds from the calculated end of totality, a dark clond swept over the corona, 
rendering all further observation impossible. 
Reduction of the Ohservations. 
The lamp used in the equatorial photometer had the values given in Table I. in 
Siemens units, reduced to a distance of 1 foot from the screen. 
Table I. 
Measures of 
potential. 
Intensity of light 
reduced to 
1 foot from screen. 
24 
•005 
23 
•007 
22 
•010 
21 
•0145 
20 
•020 
19 
•027 
18 
•036 
17 
•050 
16 
•066 
15 
•089 
The lamp was 21'25 inches from the screen during the eclipse ; hence the real 
values of the lamp were higher, but, as it is an inconvenient distance at which to 
compare the values obtained by the different instruments, an uniform distance of 12 
inches from the screen has been adopted. 
The same remark applies to the lamp used by Lieutenant Douglas. The measures 
of potential in intensity of light are given in Table II. 
Table II. 
Measures of 
potential. 
1 
Intensity of light 
reduced to 
1 foot from screen. 
1 
1 10*0 
•0024 
9-0 
•0036 
8-0 
•0040 
7-5 
•0055 
7-0 
•0074 
6'5 
•0104 
6-0 
•0135 
5-5 
•0183 
5-0 
•0258 
4-5 
•0340 
