On the Atomic Theory. 89 



smallest heating power ; close to the boundary of the red ray 

 was found a colourless ray, vviiich produced tlie greatest heat, 

 and this is a ray of caloric. The heating power of the red ray 

 and that of the violet are to each other as the following numbers : 

 the violet 16; red 55. These facts prove that the rays of the 

 sun contain free caloric as well as free light : whether the co- 

 lourless ray of caloric may contain some small portion of 

 combined light, is a question not readily solved ; it is however 

 very evident that all the rays contain more or less caloric, not- 

 withstanding the quantity separated by the prism. 



When a beam of the sun is reflected from one surface to an- 

 other, or from different surfaces, its power of heating is much 

 <iiniinished, which proves that caloric is separated from the light. 

 This tends to prove that calorific rays are not so flej:ible as those 

 of light, and that on the large scale of nature, the surface of the 

 moon reflects most of it back again in straight lines to the source 

 whence it received it, or else absorbs it, so as to withdraw it 

 from the light, which from its amazing divergency illuminates 

 the universe. Tlie first hypothesis seems to be the most pro- 

 bable. 



Many facts might be adduced to show that the hght which 

 issues from burning bodies consists of radiant heat and the light 

 itself barely mixed, and they can readily be separated from each 

 other to a certain degree by different reflectors. 



It was from turning in my mind repeatedly the facts adduced 

 in this paper, that 1 conceived the idea, that as free light and ca- 

 loric diverge from luminous bodies in company with each other, 

 sudden darkness is occasioned by the instantaneous union of 

 light to caloric, so as to form atmospheres round its particles; and 

 in my opinion there is no other rational way of accounting for 

 it. 



The first part of this paper respecting electrical phaenomena 

 and caloric was published four years ago in my Essay on the 

 Atomic Theory. I have only introduced that part of it here, 

 and in a different jjoint of view, which relates to my doctrine of 

 the coiniexion of light and caloric, which appears to me to be 

 perfectly new, according to the extent of my reading. It is 

 founded on the Atomic Theory which I presented to tlie public 

 twenty-nine years ago. At that distant period I felt that the 

 principles I set out with were well founded, as the preface to the 

 work itself will sufficiently prove : there I had predicted what it 

 lias ultimately led to ; and vet we are told in the Monthly Re- 

 view for May 1817, that I was not aware of the importance of 

 my own ideas on the subject : but I refer the learned author of 

 the paper on that sul)ject to my Comparative View, which he 

 may iiave at Mr. Murray's, bookseller, Albeniarle-street, in its 



old 



