J^<3 Ex'izmnaiion of the received DoSlrines 



an unblaffed account of the fafts they difcover. It is one of 

 the greated efforts of human probity to give them undifguifed, 

 unwarped by theory. I'his praiCe i*due to the men to whom 

 I have alkided : their labours, therefore, are invaluable, evert 

 if it fhould be provctl that, in fonie few inftances, they have 

 been miftuken in their inference?. 



It was my intention, in addition to the fafts generally 

 mentioned in my former eflay, to have brought forward, on 

 the prefent occaiion, a number of further evidences of the 

 fubflantiality of heat ; but my ftate of health, (ince our laft 

 feffion, has been fuch that I have not been able to go into a 

 wide field. I (hall, however, bring to the recollection of the 

 Society a few well-known fa6ls, which, according to my 

 liew of them^ ferve to prove that heat is a fubftance fuz 

 generis. 



Volume, as I frequently had occaflon to notice in my 

 former eflay, is a chara<!ileriftic of matter; but liquids, on 

 being mixed, are reduced in volume^ without parting with 

 any thing except heat— therefore heat is matter* 



The fame effects take place when gafcs are prcfented to 

 ^ny fubftances to which they can unite. Thus, muriatic acid 

 gas eafily combines with ice cold watery but in doing fo it 

 parts with its heat, which forms the greateft part of its vo- 

 lumci The gas is in fa6t decompofed : one of its principles, 

 the muriatic acid, joins the Water, and its other, the heat, 

 being thus fcparated from its former alTbciate, then, accord- 

 ing to the general law, firft heats the fubftances ncareft to 

 it, the acidulated water and the containing velTel, and after- 

 wards pafles off to furrounding obje6ts till equilibrium is 

 reftofed; If ice, inftead of water, be prcfented to this 

 gas, it will be melted by it as fpeedily as if thrown into the 

 fire. 



If certain gafes be united, this diminution of volume, this 

 pafling off of matter, (which^ though in union in the ingre- 

 dients, finds the capacitv^ of the new compound for it fo 

 different that it mud diffufc itfelf,) is, if polfible, ftill mord 

 ftriking. When, for example, oxvgen gas and nitrous gas, 

 in the proportions neceflary to form nitroiis acid, are pre- 

 fentcd tc> each other, in a. bell -glafs, over water; what art 



abridgement 



