M. C. Lea—Reactions of Silver Chloride and Bromide. 189 
Apart from all these things, I agree with M. Berthelot that it 
is not advisable to exaggerate the importance of these ques- 
tions, the solution of which cannot affect the important laws 
and theories of chemistry, and about which we can only reach 
a conclusion when we have arrived at more complete knowl- 
edge of the molecular constitution of compound bodies. This 
constitution itself will be doubtless revealed to us by researches 
on molecular mechanics, such as those on Thermo-chemistry, 
through which this eminent scientist aids so powerfully the 
advancement of science. ~ 
Art. XXIV.—On some Reactions of Silver Chloride and Bro- 
mide; by M. Carey Lea, Philadelphia. 
long continued action of nitric acid was there any decomposition 
of the darkened chloride, and even then, traces only of silver 
were taken up by the acid. : 
It therefore appears that the substance produced by the action 
of light on silver chloride is of a much more permanent char- 
acter than in the case of the other silver haloids) Some other 
reactions noted in the course of the examinations which appear 
not devoid of interest, are given below. 
altered substance, and completely change its character. 
As to the first point—the small proportion of material actually 
altered by light. It is generally thought that silver chloride ts 
by the action of light to a sub-chloride containing half 
