concerning Heat. 143 



be used to scratch its surface and break the glare of its 

 lustre. 



Let us return to the comparison of the evaporation 

 of water from the surface of the earth, with the emis- 

 sion of caloric radiating from the surface of a heated 

 body, and let us suppose, for an instant, that the evapo- 

 ration of the water from the surface of the earth does 

 not depend on the heat of the earth itself, but that it is 

 caused merely by the influences of surrounding bodies, 

 as, for example, by the rays of light received from 

 the sun. It is evident that, in this case, the evapora- 

 tion could not be sensibly greater in a mountainous 

 country than in the plain ; and by an easy analogy we 

 see that if hot bodies be cooled, not in consequence of 

 the emission of some material substance from their sur- 

 faces, but by the positive action of rays sent to them 

 by colder surrounding bodies, the more or less perfect 

 polish of their surfaces ought not sensibly to influence 

 the rapidity of their cooling. 



This is precisely what all my experiments concur to 

 prove. 



I have long sought, and with that patience which the 

 love of the sciences inspires, to reconcile the results of 

 my experiments with the opinions generally received 

 concerning the nature of heat and its mode of action, 

 but without being able to succeed. 



It is in the hands of two of the most illustrious 

 bodies of learned men that ever existed that I have 

 thought it incumbent on me to deposit my labours, my 

 discoveries, my doubts, and my conjectures. 



I am earnestly desirous of engaging the philosophers 

 of all countries to turn their attention towards an ob- 

 ject of inquiry too long neglected. 



