HISTORICAL REVIEW 



OF THE 



VARIOUS EXPERIMENTS OF THE AUTHOR ON THE 

 SUBJECT OF HEAT. 



A WRITER who directs the attention of the pub- 

 lic to a work upon a subject as important as it is 

 difficult of investigation must assuredly be allowed at 

 the very outset to state modestly the reasons which 

 entitle him to a hearing. It is also equally true that 

 a natural philosopher can with justice lay claim to the 

 confidence and approbation of the learned only so far 

 as his claims are based upon his own labours, upon 

 toilsome and accurate observations, as well as upon 

 experiments planned and executed with all possible 

 care. 



To engage in experiments on heat was always one 

 of my most agreeable employments. This subject had 

 already begun to excite my attention when, in my 

 seventeenth year, I read Boerhave's admirable Treatise 

 on Fire. Subsequently, indeed, I was often prevented 

 by other matters from devoting my attention to it, but 

 whenever I could snatch a moment I returned to it 

 anew, and always with increased interest. Even now 

 this object of my speculations is so present to my mind, 

 however busy I may be with other affairs, that every- 

 thing taking place before my eyes, having the slightest 

 bearing upon it, immediately excites my curiosity and 

 attracts my attention. 



