BRITISH ASSOCIATION FOR ADVANCEMENT OF SCIENCE. 675 
unto acceptation, the doctrine of a more or less analogous conception of 
heat. When we consider now the marked influence which the different 
calorific states of bodies have on their affinities — the change of crystal- 
line form effected in some by a change in temperature — the allotropic 
states taken on by some on exposure to heat — or the heat given out by 
others on their restoration from the allotropic to the ordinary form_(for 
though I am aware that Mr. Gore considers his electro-deposited anti- 
mony to be a compound, I cannot help fancying that at all events the 
state in which the antimony exists in it is an allotropic one) — when, I 
say, we consider these facts in which heat is concerned, and compare 
them with the facts of photography, and with the ozonization of oxygen 
by the chemical rays of the electric spark, and with the striking altera- 
tions in the chemical habitudes of bodies pointed out by Draper, Hunt, 
and Becquerel ; and when again we find these carried so far that, as in 
the experiments of Bunsen and Roscoe, we find the amount of chemical 
action numerically measuring the quantity of light absorbed — it seems 
hardly possible not to indulge a hope that the pursuit of these strange 
phenomena may by degrees conduct us to a mechanical theory of che- 
mical action itself. Even should this hope remain unrealised, the field 
itself is too wide to remain unexplored, and, to say nothing of discovery, 
the use of photography merely as a chemical test may prove very 
valuable, as I have myself quite recently experienced, in the evidence it 
has afforded me of the presence in certain solutions of a peculiar metal 
having many of the characters of arsenic, but differing from it in others, 
and strikingly contrasted with it in its powerful photographic qualities, 
which are of singular intensity, surpassing iodine, and almost equalling 
bromine.” 
In conclusion, Sir William noticed 
Capillary Attraction, 
remarking, that it was usually considered as belonging to 
the domain of general physics, and therefore out of this par- 
ticular department ; nevertheless, he thought it seemed to 
want attention in a chemical point of view : 
“The coefficient of capillarity differs very remarkably in different 
liquids, and no doubt also in their contact with different solids, a fact 
which can hardly be separated from the idea of some community of 
nature between the capillary force and those of elective attraction. I 
hardly dare to hint at the existence of some slight misgiving* I have 
always felt as to the validity of the received statical theory of capillary 
action, which carries with it the authority of such names as those of 
Laplace and Poisson. Any discussion of this point would be matter for 
another section of this Association ; and if 1 here touch upon it, it is 
only to observe, that my impression of the requisiteness of a force so 
far allied to chemical affinity as to be capable of saturation, rests on 
other grounds besides that of the mere diversity of action above 
alluded to.” 
