Chemistry and Physics. 131 
distracting the attention from the purely chemical questions which it 
raises, but the more we consider them in the abst th more strongly 
they force themselves on our notice, and I look forward to their occupying 
amuch larger space in the domain of chemical inquiry than is the case at 
present. That light consists in the undulations of an etherial medium, or at 
events agrees better in the characters of its phenomena with such un- 
dulations, than with any other kind of motion which it has been possible 
to imagine, is a proposition on which I suppose the minds of physicists 
are pretty well made up. e recent researches of Professor Thomson 
d Mr. Joule moreover have gone a great way towards bringing into 
vogue, if not yet fully unto acceptation, the doctrine of a more or less 
s conception of heat. When we consider now the marked in- 
strange phenom by degrees conduct us to a mechanical theory 
thane ena may by degre neoe 
f 
Covery, the use of photography merely as a chemical test may prove very 
Meet as L have myself quite recently experienced, in the evidence it 
and strikingly contrasted with it in its powerful photographic qualities, 
eh are of singular intensity, surpassing iodine, and almost equalling 
‘omMine, 
There is another class of phenomena which, though usually consid- 
ered as belonging peculiarly to the domain of general physics, and so 
artmen 
Out of our dep f, seems to me to want some attention in a chem- 
