S. P. Langley—Selective Absorption of Solar Energy. 191 
represent by H, reached the observer at noon, producing a 
deflection of 17, or 895 E = 17, giving 
ey 
: E=.,;5 = 190 
That is, had our instrument been placed outside the atmosphere 
~ that time, it would have indicated a deflection of 19 instead 
of 17. 
By a similar process we find that the coefficient of transmis- 
sion for the violet ray is -928, from which we see that the ultra- 
red ray is transmitted with greater facility than the violet. 
The amount of this violet radiation transmitted by the whole 
depth of atmosphere at noon was ‘538, from which its energy 
outside the atmosphere was 338 > 84. 
The table below gives the coefficients of transmission, etc., 
for these and other points in the spectrum where measurements 
were taken on this day. The first column gives the deviation 
of the observed ray in the spectrum of the prism used, the 
second and third columns the deflections obtained with the 
galvanometer at noon and in the afternoon, respectively, the 
fourth column the coefficient of transmission (for an atmosphere 
supporting one decimeter of mercury), the fifth the transmission 
_of the whole depth of atmosphere at noon, obtained by raising 
the coefficient of transmission to the 7°74 power, and the last 
the computed energy outside the atmosphere expressed in 
galvanometer deflections. 
TasBLE VIII. 
Deviation, ad, dy t p8 ‘ E 
3° 00’ 0-02 0-00 
52 00 0°21 0-00 
51 00 0°96 0°09 925 549 18 
50 00 45 0°39 923 538 84 
49 30 7-3 ies ents ones KOE 
49 00 13° 3°0 "953 689 18°9 
48 00 43° 12°5 980 731 58'8 
47 30 72° 38° ‘979 ‘850 7 
46 45 158° 109 938 910 173°7 
a6: 14-4 209° 134° 986 “894 233°8 
45 63 175° 107° 984 ‘883 198°3 
45 28 122: 79° 986 “895 136°2 
44 30 17 11 986 “895 
Similar reductions have been made for each day’s observa- 
tion the result from each being confirmatory of the statement 
here (see column f° #e) that the atmospheric absorption dimin- 
ishes continuously as the wave-length increases (save for the 
interruptions already cited) to the extremity of our charts. 
e graphic representation of this and other extra telluric 
curves of energy will be given in a later memoir, in such a 
