of a Mass of Matter. 205 



is for supposing it to remain constant within the same state of 

 aggregation. Within one and the same state of aggregation, 

 e. g. within the solid state, alterations in the arrangement of the 

 molecules occur, which, though without doubt less considerable, 

 are still essentially of the same kind as the alterations which 

 accompany the passage from one state of aggregation to another ; 

 and it therefore seems to me that there is something arbitrary 

 in denying for the smaller alterations what is admitted in respect 

 to the greater. On this point I cannot agree with the way in 

 which the talented English mathematician treats the subject; 

 but, relying simply on the theorem established by myself in 

 relation to the working force of heat, it appears to me that only 

 one of the following cases can be possible. Either this theorem 

 is correct, in which case the true specific heat remains the same, 

 not only for the same state of aggregation, but for the different 

 states of aggregation, or the theorem is not correct, and in this 

 case we have no definite knowledge whatever concerning the 

 true specific heat, and it may equally well be variable within 

 the same state of aggregation as in different states of aggre- 

 gation. 



§ 9. I believe, indeed, that we must extend the application of 

 this theorem, supposing it to be correct, still further, and espe- 

 cially to chemical combinations and decompositions. 



The separation of chemically combined substances is likewise 

 an increase of the disgregation, and the chemical combination of 

 previously isolated substances is a diminution of their disgrega- 

 tion ; and consequently these processes may be brought under 

 considerations of the same class as the formation or precipitation 

 of vapour. That in this case also the effect of heat is to increase 

 the disgregation, results from many well-known phenomena, 

 many compounds being decomposiblc by heat into their consti- 

 tuents — as, for example, mercuric oxide, and, at a very high, 

 temperature, even water. To this it might perhaps be objected 

 that, in other cases, the effect of increased temperature is to 

 favour the union of two substances — that, for instance, hydrogen 

 and oxygen do not combine at low temperatures, but do so 

 easily at higher temperatures. I believe, however, that the heat 

 exerts here only a secondary influence, contributing to bring 

 the atoms into such relative positions that their inherent forces, 

 by virtue of which they strive to unite, are able to come into 

 operation. Heat itself can never,- in my opinion, tend to pro- 

 duce combination, but only, and in every case, decomposition. 



Another circumstance which renders the consideration of this 

 case more difficult is this, that the conclusions we have been 

 accustomed to draw always imply that the alterations in ques- 

 tion can take place in a constant and reversible manner ; this, 



