45 



theory of latent heat. He has poured the whole force of his eloquent 

 panegyric on the practical results of the labours of the great engineer, 

 and the mechanical ingenuity displayed in them ; but he might have 

 pointed to the early and profound attention which he devoted to this 

 theory, as the fountain-head of his fame, and shown him in the acade- 

 mical class room, and the laboratory, of Black, imbibing that spirit, 

 and advancing those principles of science, which were afterwards em- 

 bodied in all his works, and gave life to all his inventions ; and he might 

 thus have taught us, in a manner worthy of his own genius, what it is 

 more especially, that entitles Watt, rather than Worcester or Papin, 

 Savery or Newcomen, to be admired as the philosophical parent of 

 the gigantic and diversified powers of the steam-engine. 



APPENDIX. 



EXTRACTS FROM THE CAVENDISH MSS. REFERRED TO IN THE 

 FOREGOING POSTSCRIPT. 



EXPERIMENTS ON HEAT. 



[When an edition of the works of Cavendish is published, (as I believe is 

 intended), I hope that these papers on heat will be printed at large with all 

 the experiments. I have here confined myself to extracting such passages as are 

 suflScient to substantiate what I have advanced in the Postscript to my Address. 

 The treatise containing these views, and the general result of the experiments, 

 was written for the use of some individual, it does not appear whom. The 

 same is the case with respect to the experiments on arsenic, which follow : 

 and the date of both these remarkable series of experiments appears to be about 

 the same, that is to say, certainly not later than 1764 : as with respect to those 

 on heat the following extract, copied verbatim from the original notes (p. 89) 

 of the experiments, shews. 



" Feb. 5, 1765 : — therm, in room about 35 : heat of liquors in bottles, 34 : 

 the weight of the bottles with the liquors was known : the liquors were put 

 into wide-mouthed vessels inclosed in wool, the weight of the glasses being 

 known; & snow added till therm, sunk to about 19 : the snow seemd not 

 at all inclinable to melt when taken up, & was put in glass vessel set in mix- 

 ture of snow & salt water : the heat of snow when made use of was neg- 

 lected to be tried : the solution of sea- salt sunk to 18^, the spt of wine 

 to 19, the f. alk. to 22, & the aq. fort, to 19 : the spt of salt was not 

 tried. After the experiment was finished, the wide-mouthed glasses with 



