43 
increasing numbers, giving the chemical intensity (I.) of 
total daylight occurring during the eclipse for the apparent 
solar times indicated : 
Time. 
i. 
Time. 
i. 
7h. 57m.... 
...0-590 
9h. 0m. . . . 
...0-005 
8h. 8m. . . . 
...0-320 
9h. 15m.... 
...0-102 
8h. 16m 
...0-270 
9h. 25m.... 
...0-140 
8h. 28m.... 
...0-110 
9h. 31m 
...0-125 
8h. 45m.... 
...0-090 
In order to determine how far these values of chemical 
intensity correspond to the numbers giving the relative areas 
of the solar disc remaining uneclipsed, it is necesary in the 
first place to allow for the variation in chemical intensity 
caused by alteration in the sun’s altitude from the time of 
first contact at 7h. 44m, 6s. until the point of last contact at 
lOh. 21m. 7s. On a former occasion (Phil. Trans. 1867, p. 
559) I have shown that the relation between the sun’s alti- 
tude and the chemical intensity, is represented by the 
equation 
CI a = CI 0 + Const, x a. 
Where CI a signifies the chemical intensity at any altitude 
(a) in circular measure, CI 0 the chemical intensity at the 
altitude 0°, and Const, is a number to be calculated from the 
observations. In default of any special series of experiments 
made at J amkhandi for the purpose of ascertaining the value 
of the constant at that place, I take the determinations 
made at Para (loc. sit.) (in lat. 1° 25’ S.) as probably giving 
a fair approximation to the truth, for I have shown in the 
paper above referred to that even for places so differently 
situated as Heidelberg and Para no very great difference 
exists in the value of the constant. 
In the following table the relation of the chemical in- 
tensity to the sun’s altitude is seen in column IV. when the 
intensity at the highest altitude, 53° 1 o', is taken as the unit. 
Column V. contains the values of I. corrected for variation 
of altitude, and column VI. contains the relative areas of 
the sun’s disc remaining uncovered at the corresponding 
apparent solar time found in column I., the area of the solar 
