REGISTBATION OF THE CHEMICAL ACTION OF TOTAL DAYLIGHT. 
607 
Table I. 
I. 
Millims. 
II. 
Seconds. 
I. 
Millims. 
II. 
Seconds. 
I. 
Millims. 
n. 1 
Seconds. 
I. 
Millims. 
II. 
Seconds. 
I. 
Millims. 
II. 
Seconds. 
I. 
Millims. 
II. 
Seconds. 
0 
1-200 
32 
1-003 
64 
0-846 
96 
0-700 
128 
0-549 
160 
0-369 
1 
M93 
33 
0-998 
65 
0-841 
97 
0-695 
129 
0-544 
161 
0-363 
0 
1-186 
34 
0-993 
66 
0-837 
98 
0-691 
130 
0-539 
162 
0-357 
3 
1-179 
35 
0-988 
67 
0-832 
99 
0-686 
131 
0-534 
163 
0-350 
4 
1*1 72 
36 
0-983 
68 
0-828 
100 
0-682 
132 
0-528 
164 
0-343 
5 
1-165 
37 
0-977 
69 
0-823 
101 
0-677 
133 
0-523 
165 
0-336 
6 
1-158 
38 
0-972 
70 
0-819 
102 
0-672 
134 
0-518 
166 
0-329 
7 
1-151 
39 
0-967 
71 
0-814 
103 
0*668 
135 
0-513 
167 
0-321 
8 
1-144 
40 
0-962 
72 
0-809 
104 
0-663 
136 
0-508 
168 
0-314 
9 
1-137 
41 
0-957 
73 
0-805 
105 
0-659 
137 
0*502 
169 
0-309 
10 
1-131 
42 
0-952 
74 
0-800 
106 
0-654 
138 
0-497 
170 
0-300 
11 
1-125 
43 
0-947 
75 
0-796 
107 
0-650 
139 
0-492 
171 
0-291 
12 
1-119 
44 
0-942 
76 
0-791 
108 
0-645 
140 
0-487 
172 
0-283 
13 
1-113 
45 
0-937 
77 
0-786 
109 
0-640 
141 
0-482 
173 
0-274 
14 
1-106 
46 
0-932 
78 
0-782 
110 
0-635 
142 
0-476 
174 
0-266 
15 
1-100 
47 
0-927 
79 
0-777 
111 
0*631 
143 
0-470 
175 
0-257 
16 
1-094 
48 
0-922 
80 
0-773 
112 
0-626 
144 
0-465 
176 
0-249 
17 
1-087 
49 
0-917 
81 
0-768 
113 
0-621 
145 
0-459 
177 
0-240 
18 
1-081 
50 
0-912 
82 
0-764 
114 
0-617 
146 
0-453 
178 
0-229 
19 
1-076 
51 
0-907 
83 
0-759 
| 115 
0-612 
147 
0-448 
179 
0-219 
20 
1-070 1 
52 
0-903 
84 
0-755 
116 
0-607 
148 
0-442 
180 
0-208 ! 
21 
1-064 
53 
0-898 
85 
0*750 
117 
0-603 
149 
0-436 
181 
0-198 j 
22 
1-058 
54 
0-893 
86 
0-745 
118 
0-598 
150 
0-431 
182 
0-187 
23 
1-053 
55 
0-888 
87 
0-741 
119 
0-593 
151 
0-425 
183 
0-176 I 
24 
1-047 j 
56 . 
0-884 
88 
0-736 
120 
0-588 
152 
0-419 
184 
0-161 
25 
1-041 
57 
0-879 
89 
0-732 
121 
0-583 
153 
0-413 
185 
0-146 
26 
1-036 
58 
0-874 
90 
0-727 
122 
0-578 
154 
0-407 
186 
0-131 
27 
1-030 
59 
0-870 
91 
0-723 
123 
0-573 
155 
0-401 
187 
0-116 
28 
1-025 I 
60 
0-865 
92 
0-718 
124 
0-568 
156 
0-394 
29 
1-019 
61 
0-860 
93 
0-714 
125 
0-563 
157 
0-388 
30 
1-014 
62 
0-856 
94 
0-709 
126 
0-558 
158 
0-382 
31 
1-009 
63 
0-851 
1 
95 
0-704 
1 127 
0-553 
159 
0-376 
tint to two points on the unfixed strip situated 10 millims. on each side of this, were 
found to be 100 millims. and 123 millims; (3) by reference to the Table, the relation 
between the intensities on these two positions is found to be as 0672 to 0578; 
(4) these numbers, multiplied by q t the reciprocal of the intensity corresponding to 
112 millims., give the intensities expressed in terms of the unit formerly employed, 
which acting for one second produce the tints in question. 
The method of observation thus becomes very simple. To each of the fixed and 
graduated strips an Intensity Table is attached, giving the value of the tints upon each 
millimetre of its length in terms of the described unit ; a piece of standard sensitive 
paper is exposed for a known number of seconds to the light which it is required to 
measure, until a tint is attained equal to some one of the tints upon the strip ; the 
exact position upon the strip of equality of tint to the exposed paper is next read off by 
the light of the soda-flame ; the number found in the Intensity Table opposite to this 
position, divided by the time of exposure in seconds, gives the intensity of the acting 
light in terms of the required unit. 
A detailed description of the apparatus employed, and of the methods of preparing 
and graduating the strips, will be given under separate headings. 
4 o 2 
