44 
disc before the commencement of the eclipse being taken as 
the unit. 
Apparent Solar Time. (I.) Altitude. 
I. II. Ill, IV. V. VI. 
7h. 57m. ... 0-590 ... 30° 30' ... 0-622 ... 0-948 ... 0-94 
8h. 8m. ... 0-320 ... 33° 30' .. 6*671 ... 0-476 ... 0-71 
8h. 16m. ... 0-270 ... 35° 0' ... 0-705 ... 0-383 ... 0-62 
8h. 28m. ... 0-110 ... 38° 30' ... 0-753 ... 0-146 ... 0-43 
8h. 45m. ... 0-090 ... 42^30' ... 0-820 ... 0-100 ... 0-17 
9h. 0m. ... 0-005 ... 46° O' ... 0-885 ... 0-005 ... 0-00 
9h. 15m. ... 0-102 ... 49° 45' ... 0-933 ... 0-109 ... 0-21 
9h. 25m. ... 0-140 ... 52°, O' ... 0-966 ... 0-145 ... 0-37 
9h. 31m. ... 0-125 ... 53° 15' ... 1-000 ... 0-125 ... 0-49 
The curve A repre- 
sents the variation of 
chemical intensity cor- 
rected for altitude, and 
the curve B shows the 
increase and diminu- 
tion of obscuration of 
the sun’s disc, the ab- 
scissse representing the time and the ordinates, the corres- 
ponding chemical intensity and area of exposed disc. The 
observations unfortunately could not be carried on, owing 
to cloud, beyond 9h. 23m., at which time the sun’s disc was 
still more than half eclipsed, so that the rise of the curve 
beyond this point cannot be given. 
If we compare the curve of chemical intensity which is 
nearly symmetrical on both sides of the totality, with the 
curve of solar obscuration, it will be seen that the rate of 
diminution of the chemical intensity of total daylight during 
the first portion of the eclipse up to the point at which the 
disc is half obscured is greater than corresponds to the area 
of darkened solar disc, whilst from this point up to totality 
the rate of diminution of chemical action is much less than 
that of the exposed portion of the disc. 
Determinations were also made from time to time with 
the arrangement for shading off' all the direct sunlight from 
the sensitive paper, and these combined with alternate 
