DECOMPOSITION OF WATER BY HEAT. 327 



force by which many compounds, and particularly water, could 

 be resolved into their constituents without either of these 

 being absorbed by another affinity. The decomposition by 

 ignited platinum removes this exception, and presents the 

 parallel effect produced by heat alone. 



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 substances 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 repulsion of the molecules 

 of matter ; and if heat produce effects of decomposition merely 

 by increase of intensity, 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 inde- 

 finitely 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 condition of matter. 



