S,\% Examination of the received DoS! fines 



this cafe will be, if denominated by its volume, exatlly of the 

 bulk of the capacity of the veffel. If the veffel has been 

 charg' d with a quantity of gas equal in bulk to three times 

 its own capacity, the heat forced out will be equal in hulk to 

 twice that capacity ; and fo of any other proportion of charge. 



Here, then, the fame effect takes place as when wc con- 

 fine fteam ; the means are mechanical in both ; the heat is 

 fqueezed out through the ikies of the veffel by the force em- 

 ployed, as water is fqueezed from a fpunge by preffure ap- 

 plied to it. Was the water in the fpunge of a different na- 

 ture before and after being expreffed, firft latent and then 

 fenlible ? If it would be abfurd to fay fo, why mould wc fup- 

 pofe heat, when diflodged by fimilar means, to have under- 

 gone any change as to its nature, and to have been latent 

 before but jenfible after ? meaning thereby that iis character-. 

 iftic properties were different before and after the proeefs. 



But have we any experiments that prove heat to be actually 

 feparated by mechanical force from fubftances in which it is 

 held to be latent or in chemical union? When the condenfer 

 of an air-gun, or any other proper veffel, is charged with 

 more than one atmoipherc, the materials, as the proeefs goes 

 on, become of a higher temperature than the unrounding 

 bodies*, and heat is given off to them. This (hows that 

 heat ;s expreffed from the contained air; and that, not being 

 able to pafs freely, but forced to pafs more or lefs flowlv, 

 according to the conducting power of the materials of the 

 veffel, it is partially accumulated in the materials, and then 

 from them paffed off to furrounding bodies to reflore equili- 

 brium according to the general law. 



If the wall of feparation, which forces the confined gas tq 

 remain charged with a fmaller quantity of heat than its con- 

 ftitution would permit, but for the violence employed, be 

 removed, what takes place? The gas inftantly feizes upon 

 a portion of the caloric employed in maintaining the common 

 temperature of the furrounding bodies, fitted to its own ca- 

 pacity in its unrcftraincd ftate, and in confequencc refumes 

 its original volume. This plainly appears to be the cafe, 



* Sec Dr. Darwin's pnper on this fubjeci, Philosophical Tranfaftions 

 fpr 17ft! 



for 



