Experimenis on the Heat txditi hy FriSlim. xf] 



is excltCf!, continued, and propagated 5 and I fhall not prefunne to trouble the Society with 

 mere conjeftures, particularly on a fubjedl which, during fo many thoufand years, the 

 mofl enlightened philofophers have endeavoured but in vain to comprehend. 



But although the mechanifm of heat (hould in fadl be one of thofe myflerles of nature 

 which are beyond the reach of human intelligence, this ought by no means to difcourage 

 us, or even leflen our ardour, in our attempts to inveftigate the laws of its operations. How 

 far can we advance in any of the paths which fcience has opened to us, before we find 

 ourfelves enveloped in thofe thick mills which on every fide bound the horizon of the hu- 

 man intelledt ? But how ample and how interefting is the field that is given us to explore! 



Nobody, furely, in his fober fenfes has ever pretended to underftand the mechanifm of 

 gravitation ; and yet what fublime difcoveries was our immortal Newton enabled to make, 

 merely by the inveftigation of the laws of its aftion ! 



The efFefts produced in the world by the agency of heat are probably yw^ as extenftve, 

 and quite as important, as thofe which are owing to the tendency of the particles of matter 

 towards each other ; and there is no doubt but its operations are in all cafes determined 

 by laws equally immutable. 



Before I finifli this paper I would beg leave to obferve, that although, in treating the 

 fubjeft I have endeavoured to inveftigate, I have made no mention of the names of thofe 

 who have gone over the fame ground before me, nor of the fuccefs of their labours; this 

 oniiffion has not been owing to any want of refpe£t for my predeceflbrs, but was merely 

 to avoid prolixity, and to be more at liberty to purfue without interruption the natur^ 

 train of my own ideas. 



Defcription of the Figures. Plate V. 



FIG. 1. (hows the cannon ufed in the foregoing experiments, in the ftate it was when it 

 came from the foundry. 



Fig. 2. (hows the machinery ufed in the experiments No. i. and No, 2. The cannon is 

 feen fixed in the machine ufed for boring cannon. W is a ftrong iron bar (which, to 

 fave room in the drawing, is reprefented as broken off ) ; which bar being united with ma- 

 chinery (not expreiTed in the figure) that is carried round by horfes, caufes the cannon to 

 turn round its axis. 



»w is a ftrong iron bar, to the end of which the blunt borer is fixed, which, by being 

 forced againft the bottom of the bore of the fliort hollow cylinder that remains conne^led 

 ty a fmall cylindrical neck to the end of the cannon, is ufed in generating heat by fri£lion. 



Fig. 3. fhows on an enlarged fcale the fame hollow cylinder that is reprefented on a 

 fmaller fcale in the foregoing figure. It is here feen connefted with the wooden box 

 {gi h, /, k) ufed in the experiments No. 3. and No. 4. when this hollow cylinder was im- 

 merfed in water. 



p, which IS marked by dotted lines, is the pifton which clofed- the end of the bore of the 

 cylinder. 



« is the blunt borer feen fideways. 



</, e, is the fmall hole by which the thermometer was introduced, that was ufed for af- 

 certaining the heat of the cylinder. To fave room in the drawing, the cannon is repre- 

 fented broken oflF near its muzzle ; and the iron bar, to which the blunt borer is fixed, is 

 xeprefented broken oS^tm, 



Tig. 



