INTENSITY OP CORONAL LIGHT DURING THE SOLAR ECLIPSE OF 1893. 439 
the precipitation of moisture after the first 60 or 70 seconds of the totality ; dark 
clouds rapidly gathered in the neighbourhood of the disc, and at about one minute 
before the calculated end of the total phase the moon and corona were wholly 
obscured. The air was saturated with moisture ; a slight shower had indeed fallen a 
few minutes before the beginning of totality, and the lowering of the temperature, 
consequent on the obscuration of the solar disc, undoubtedly caused the gradual 
condensation of moisture. Hence, therefore, we could only regard, at most, the first 
six out of the possible sixteen observations made with the equatorial photometer as 
valid ; and only three, at the outside, out of the sixteen readings made by the 
integrating photometer were of any value as measuring the total brightness. 
On the present occasion, owing to the much more favourable conditions, the 
greater number of the measurements made by the equatorial photometer, twenty in 
all, as well as ten measurements made by Mr. Forbes with the integrating photo¬ 
meter, are available. The results of these measurements are given in the following 
tables :—Table I. gives the value in light of the readings of the equatorial photo¬ 
meter. The numbers of grease-spots in Column I. correspond with the order in 
which they were read. Column II. gives the calculated distance of each spot from 
the sun’s centre in terms of the solar semi-diameter. Column III. gives the readings 
on the ammeter ; and Column IV. the corresponding value of the light in Siemens’ 
units at one foot. Column V. gives the approximate time in seconds after the 
beginning of totality when the readings were made. 
Table I.—Headings on the Equatorial Photometer reduced to the value of 
Light-Intensity. 
I. 
II. 
III. 
1Y. 
V. 
1 
1-66 
1060 
•058 
10 
2 
2-70 
1-015 
•037 
16 
*> 
o 
3-80 
•954 
•018 
23 
4 
1-30 
1-070 
•061 
30-5 
5 
2-88 
1-021 
•038 
42 
6 
312 
•951 
■019 
48-5 
7 
1-76 
1-186 
•137 
61 
8 
2-32 
•969 
•023 
71 
9 
■ 3-28 
•928 
■015 
79 
10 
1-70 
1-088 
•069 
92 
11 
2-82 
1-020 
039 
1015 
12 
3-88 
•961 
•021 
107 
13 
2-46 
•950 
•018 
121 
14 
2-46 
•920 
•013 
131 
15 
2-42 
•877 
■009 
141-5 
16 
2-64 
•950 
•018 
151 
1 
1-66 
1-110 
•084 
162 
4 
1-30 
1060 
•058 
172 
7 
1-76 
1-170 
•123 
185 
10 
P70 
1-030 
•042 
193-5 
