Chemistry and Physics. A17 
by a lens, was received upon a white tablet and submitted to careful 
resentation of the connexion between the color of a ray, and its power 
to produce chemical change. In the report made to the Belfast Meet- 
ing of the British Association the results of experiments made upon glass 
tablets prepared by the so-called collodion process were alone given. 
In the present report the examination has been extended to the photo- 
graphic preparation known as the calotype, and iedid and bromid of 
silver in their pure states and when excited by gallicacid. _M. Edmond 
i A 
are m rptive media which, at the same time as they obliterate 
a particular colored ray, destroy the chemical action of that portion of 
the spectrum, yet there are a still more extensive series which prevent 
the passage of a ray of given refrangibility, and do not at the same 
Srconp Serres, Vol. XVI, No, 43.—Nov., 1853. 
