KEGISTKATION OF THE CHEMICAL ACTION OF TOTAL DAYLIGHT. 611 
Graduation of fixed strip A. 
Position of standard tint upon pendulum strip No. 1 = 85 millims., from which the 
constant zr~ -z is found in Table I. p. 607. 
0*750 A 
The position 20 mm. on pendulum strip =1*427 intensity, and corresponds to 67*4 mm. on fixed strip. 
40 
, 1-283 
„ 79-8 
„ 
60 
, 1-154 
„ 83-0 
„ 
80 „ 
1-031 
„ 91-6 
„ 
100 
0-910 
„ 94-5 
„ 
120 
0-784 
„ 119-8 
„ 
140 
0-650 
„ 121-6 
„ 
In like manner the constants for three other pendulum strips were determined. 
Constant for pendulum strip No. 2= 0 .^ -- 
Constant for pendulum strip No. 3=^^-* 
Constant for pendulum strip No. 4= Q .^ Q -- 
By comparison of each of these three pendulum strips with the fixed strip the follow- 
ing numbers were obtained. Column I. gives the readings on the millimetre-scale of 
the fixed strip ; Column II. the corresponding intensities calculated as in the foregoing 
example. 
Wo. 2. 
No. 3. 
No. 4. 
I. 
II. 
I. 
II. 
I. 
II. 
26-0 
2-12 
49-9 
1-76 
34-6 
2-10 
35-3 
1-90 
60 0 
1-59 
40-4 
1-89 
55-5 
1-69' 
70-5 
1-43 
53-4 
1-70 
72-6 
1-47 
81-5 
1-27 
64-8 
1-52 
80-1 
1-25 
92-4 
M2 
82-5 
1-16 
90-5 
1 00 
103-0 
0-97 
93-0 
0-96 
121-4 
0-80 
123-6 
0-72 
131-5 
0-61 
In order to obtain the mean result of these numbers, the curve for each of the four 
graduations was drawn, the abscissae giving the positions on the fixed strip in millimetres, 
and the ordinates the intensities corresponding to these positions. A curve was then 
interpolated, lying as nearly as possible between the points determining the single obser- 
vations, and from this mean curve the intensity for each millimetre on the scale was 
calculated. The following are these tabular values for every 10 millims. Column I. 
gives the position in millims. on the fixed strip, Column II. the corresponding intensity, 
and Column III. the mean tabular error. 
