On Chemical Vhilosophy. 347 



formed this a:do!Ti, " that whenever a hody changes its slates, it 

 either comhhies with or separates fnm caloric." This has beea 

 found true to a much greater extent than was ascertained during 

 tlie time of Dr. Black. His attention in forming this conclusion 

 seems to have been chiefly directed to changes from the sohd to 

 the liciiiid, and from the liquid to the solid states. But it is now 

 dearly shown, however slight the change in any one of these 

 states, and however produced, — whether mechanically or chemi- 

 cajly; whether by compression or tlie removal of pressure; in al- 

 most all instances of mixing substances together, and the solu- 

 tion of substances in liquids ; and in all wliere the resulting den- 

 sity of the compound is not tlie mean between them in their se- 

 parated states, — a proportionate quantity of this power in one 

 form or another is either given out or absorbed : suhstonces give 

 it out or demaiid it, in proportion as they are relatively to each 

 other 771 excess, or defective. 



I.s it not then most evident, that " all changes are mere ex- 

 changes of this poiver," passing from one substance into an- 

 other; separating from this, in order to dissolve and combine 

 with some other species of matter ? and in proportion to their 

 solubility or insolubility they are united or separated from each 

 other ; and this in a more or less perfect and striking manner, 

 in a greater or less degree, according to the nature of the sub- 

 Btances, and the extent of the changes produced. 



If then the science of chemistry endeavours to ascertain the 

 laws and principles of that power which produces all the motion 

 and union of matter, we have to explain what have been consi- 

 dered very different and opposite kinds of effects and phceno- 

 mena ; and this is still the production of the same power, and 

 not, as has been considered, effects and pha;nomena belonging 

 to another and opposite power, called repulsion. It therefore 

 becomes necessary to state in what, according to my opinion, this 

 difference consists. It depends, I conceive, on different degrees 

 of the same power; which different degrees prod';ce various ef- 

 fects, according to the circumstances in which, and the substances 

 on which, it operates. In fact, in proportion to the quantity of 

 this power and the time taken to act, and the solubility of the 

 substances on which it acts, it tends more or less to change their 

 Jitate of existence. The quantity necessary to produce this 

 change is equally necessary to support this change. Chemists liavc 

 called this their relative capacity; as if water and steam difTered 

 in any way, and in the relative quantity of this power required 

 for their respective states of existence. That water in the state 

 called steam, occupies arid .suspends the active energies of this 

 power, is evident from this fact, — that this gas or vapour does not 

 scald more than air heated to that temperature \ but when the 



water 



