MR. GROVE ON THE DECOMPOSITION OF WATER BY HEAT. 
15 
Although there is no substance except platinum and some of the more rare metals, 
such as iridium, which promise much success in a laboratory experiment made for 
the purpose of producing the effect I have described, as the greater number of sub- 
stances which will bear a sufficient heat, are fragile, oxidable, or affected by water, 
yet general considerations from the nearest analogies in chemistry would lead us to 
expect a similar effect from all matter in a state of intense ignition even assuming 
the presence of solid matter to be necessary, the catalytic effects of platinum are 
shared in different degrees by other substances : it therefore appears probable that at 
a certain degree of heat water does not exist as water or steam, but is resolved into 
its constituent elements. If, therefore, there be planets whose physical condition is 
consistent with an intense heat, the probability is, that their atmosphere and the 
substances which compose them are in a totally different chemical state from ours, 
and resolved into what we call elements, but which by intense heat may be again 
resolved into more subtle elements. The same may be the case in the interior of 
our planet, subject however to the counter agency of pressure. 
The experiments strongly tend to support the views of Berthollet, that chemical 
and physical attraction are affinal, or produced by the same mode of force. All 
calorific expansions appear to consist in a mechanical severance of the molecules 
of matter ; and if heat produce effects of decomposition merely by increase of inten- 
sity, there seems no reason why we should assign to it in this case a different mode 
of action from its normal one. On this view physical division carried on indefinitely 
must ultimately produce decomposition, and chemical affinity is only another mode 
of molecular attraction. Thus a high degree of rarefaction, as at the bounds of the 
atmosphere, or in the interplanetary spaces, may entirely change the chemical condi- 
tion of matter. 
In a paper published in the Philosophical Transactions for 1843, p. Ill, I have 
shown that we may oppose a chemical action by a physical one (electrolysis by a 
vacuum), that antagonizing chemical by physical tension, they mutually oppose each 
other. I believe the converse of this experiment has been made by M. Babinet, who 
by physical compression has prevented the development of chemical action. 
I have also described in the Philosophical Magazine for November 1845, certain 
phenomena which appear to me to be irreconcileable with received chemical views ; 
and though I then believed that the theory of Grotthus would be obliged to give 
way, I now incline to think that some of our chemical doctrines must ere long un- 
dergo a revision. 
It is rather surprising that the valuable applications of which the phenomena of 
voltaic ignition are capable, and the fertile field which (as I believe) it presents for 
discoveries, both physical and chemical, should have been so completely neglected. 
It is true that until a recent period the imperfection of the voltaic battery rendered 
accurate and continued experiment on this subject difficult of performance, but still 
much might have been done. Davy made several experiments on the voltaic disrup- 
