270 M. C. Lea—Action of the less refrangible rays of Light 
spectrum the sensitiveness of both the compounds in question, 
especially of silver iodide. 
The second of these positions, that in reference to the com- 
parative sensitiveness of AgI and AyBr, differs essentially from 
the views hitherto accepted, according to which AgBr has been 
held to be by far the more sensitive to the less refrangible rays. 
[ shall endeavor to show that the contrary is the case. 
In these investigations I have confined myself to studying 
the effects obtained upon the silver compounds as formed in the 
body of pure paper, applying in all cases the silver solution 
after that of the alkaline haloid, and immediately washing out 
the excess of silver nitrate. 
ously managed with the solar spectrum than with colored glass. 
Still another advantage in the use of colored glass is that 
the pieces used can be of any desired size, so that one cap 
operate over a large space and can simultaneously expose sev: 
per, the effects of the exposure are rendered much more marked: 
