64 



Captain W. de W. Ahney 



[March 17, 



Your attention should be drawn more especially to the water 

 spectrum, in which it will be seen what a large proj)ortion of the 

 infra red is cut off by even a small thickness. Aqueous vapour 

 absorbs in the same locality as the water ; hence you will see 



Fio. 4. 



1000 1100 



CARBON DISULPHIDE 



i liiiiiijiiiiiiiliiiii 



CHLOROFORM 



yi^^idi^dti^iW 



METHYL IODIDE 



MiniiiniiiiMiiii 



ETHYL IODIDE 



dii'i^dd 



BENZINE 



AMYLENE 



ETHER 



ALCOHOL 





WATER 



how it is that I have photographed the bands cf> and ip in the solar 

 spectrum but seldom (see Fig. 2). When they were impressed a very 

 dry and biting north-east wind was blowing, which enabled this part 

 of the spectrum to find its way through our atmosphere. 



On comparing the solar spectrum with the absorjition spectra of 

 the above organic bodies, we found that the principal lines of the 

 benzine and ethyl scries found a place in the solar absorptions ; and 

 for reasons which I have not time to enter into now, we were induced 

 to locate these bodies outside our atmosphere. In what part of space 



