HEAT AND LIGHT IN THE ATMOSPHERE. 71 



in excess in the presented surface of infixed body ; and when 

 light falls on it, all the other rays are absorbed. 



The evidences in support of the position will be adduced in 

 their proper place. 



The absence of caloric, in the instance of reflected light, 

 may account for the latter's being incapable of refrangibility. 



The energy with which caloric is communicated, is increased 

 by pressure, producing closer contact. 



The intensity of light produced by the combustion of fixed 

 bodies, is proportional to the elevation of temperature acquired, 

 which is influenced by the energies with which the material 

 rays enter into combination ; and this is variable, according to 

 the particular circumstances under which they are presented. 



When chemical combinations are formed by bodies in a fixed 

 state, heat is evolved or absorbed ; but generally no change to 

 that of the radiant state is effected without combustion. 



But when from the mutual action of bodies combustion 

 arises, there is an absolute transition of a certain portion of 

 fixed matter to the radiant state, and the residuum is fixed 

 matter, the qualities of which are generally quite different from 

 those it possessed in its previous form ; that difference arising 

 either from the acquisition of the matter of some ray or rays, of 

 which it was deficient, or the abstraction of others with which it 

 may have been originally replete. 



Heat and light both exist in the atmosphere ; \\\e former, but 

 a modification of the latter, is the active agent of combination 

 between the light in its perfect state, and fixed, or inert 

 matter. 



Light is evident to us when it emanates direct from a point 

 of radiation, and continues visible during the existence of that 

 point as a centre of action, and therefore appears to be governed 

 by the effects of pressure. 



But the production of light does not rest on its separation 

 as a specific body from oxygen, or the atmosphere, by the act 

 of combustion, as it was supposed by M. Lavoisier, who also 



