I 



re/peeling Heat or daloric. i5i 



ftt)riclgment of volume takes place ! It cannot be oiherwifcj 

 the capacity of the new compound for heat being fo much 

 lefs than the fum of that of the ingredients ; for the mole- 

 culse now refpe6tively arrange thcmfelves with each other in 

 fuch a manner, that they can afford but a fmall quantity or 

 Jodging-room for the heat, compared with what it occupied 

 in the gafes ; and it is therefore forced, by the general law^ 

 to diifufe itfclf among and through the contiguous bodies til! 

 each is with each in equilibrium* But each th<jreby receives 

 an increafe of volume, that is, an increafe of matter 5 and it 

 is extremely probable that, if we could get at the fum of 

 their increafe, it would be found exactly equal tb the differ- 

 ence between the volume of the gafes before mixture and 

 that of the acid produced. 



If any quantity of nitrous gas be joined to twice its bulk 

 of atmofpheric air, we all know that the fame effe^ls take 

 place as in the cafe jufl mentioned ; that is, the fubiiance 

 ijeat changes its affociates. 



We may obferve here that, as heat pafTes freely through all 

 bodies, and tends to an equilibrium 5 and as this equilibrium^ 

 when cftablifhed in any fyftem of bodies, is fometimes higher 

 than at others, it feems far from being correal to talk of heat 

 being then in ajlate of conjineynent. If a colder body be made 

 one of this fyftem it will foon be feen that the heat, inftead 

 of being latent in the other bodies, finds \\,M^ free to pafs 

 from them into the colder body till it has received the por- 

 tion fuited to its capacity compared with that of the others. 



If there be any ftate in which heat is Icfs in a (late of con- 

 finement than another, it is when in equilibrium ; and it is 

 only when it has, by any means, been accumulated in indi- 

 vidual bodies, in greater proportion than, by their capacity^ 

 compared with that of the furrounding bodies^ they ought to be 

 fupplied with, that any thing like reftraint can be confidered as 

 impofed upon it. The impediments that retard its equal dif- 

 fufion, are, in fa^fc, the only reftraints it experiences ; and to 

 me this appears fo obvious, that I cannot help wondering 

 how men of fcience (hould ever have thought of calling it 

 Jree in fuch circumftances. It i^free, to be fare, but not in 

 iheir fenfe of the word; for it has refUaiius to overcome ; but 

 Vol, IX, X when 



