184 S. P. Langley—Selective Absorption of Solar Energy. 
giving the wave-lengths of lines for which he derives by an 
extra-polation curve a position at A = 1"-240, and indicating a 
band still beyond. 
Captain Abney had previously published a map of the 
diffraction spectrum extending to 4= 0"-9682. Dr. J. W. 
Draper,” by the aid of Captain Abney’s map, believes he has 
identified the lines a, PB, 7 he saw in 1842 with groups repre- 
sented by Abney at 4 = 0"-8150 to 0"-8350, 0":8930 to 0"-9300, 
and 0":9350 to 0"-9800. 
On our chart we have given Draper's a, , 7 according to his 
own locations of them. He believes these to be the same lines 
seen by himself, Foucault and Fizeau, and Lamansky. Ac 
cording to Draper, then, the lowest limit of his own or any 
other researches known to him in 1881, did not extend much 
beyond wave-length 1”:0000. It appears to us probable, how- 
ever, that Lamansky’s lowest point was below this, and we 
give a copy of Lamansky’s curve (fig. 8) which the reader can 
compare with the positions on our present charts. 
3. 
- * * D cine 
LAMANSKY. 
These brief references concern only what belongs to our im- 
mediate purpose, and are not offered as a history of the subject. 
RECENT OBSERVATIONS ON THE INVISIBLE PRISMATIC 
PECTRUM. 
After the return from Mt. Whitney, observations were taken 
at Allegheny with the train of apparatus used on the mountain 
just referred to, and on nearly every good day during the first 
six months o , ese were of such: 4 days in January, 
8 in February, 9 in March, 9 in April, 9 in May, 12 in June. 
In all, 51 days. 
" Proceedings of the Amer, Acad., 1881. 
