HEAT OR CALORIC. 43 



ing rays; but it has not been ascertained that the de-oxidizing chem- 

 ical rays are present.* 



15. The physical laws of all the three varieties of rays are nearly 

 the same, differing a little in the amount of the effect. 



(a.) They are refrangible ; this is proved by their passing through 

 the prism, and being all made to deviate from their course. 



(6.) They are refrangible in different degrees ; and this is true, 

 whether we compare one sort of rays with another, or the rays of 

 one kind individually among themselves. 



(c.) Some rays of each kind are equally refrangible, and are there- 

 fore found in company through the whole spectrum. 



(d.) Some rays of caloric are less refrangible than any of the 

 other rays of either kind ; therefore they are found outside of the 

 red rays in the dark. 



(e.) Some of the chemical rays are more refrangible than any 

 other, of either kind ; hence they are found outside of the violet ray, 

 and in the dark. 



(/.) The spectrum, then, is composed of the three sorts of rays, but 

 it is terminated by calorific rays on one side, and by chemical rays 

 on the other ; on both wings it has opake rays, but of different kinds. 



(g.) Jill the kinds of rays are reflexible. This is evident from the 

 effect of mirrors ; and Scheele long ago, ascertained the equality of 

 the angles of incidence and reflection. 



(h.) At a given distance from the radiant point, the intensity of 

 both heat and lightf is inversely as the square of the distance, e. g. 

 At the distances 2, 3, 4, it is as 4, 9, and 16 inversely. 



16. It is probable that all the three kinds of rays are emitted from 

 the sun, and other sources with equal velocity. 



We are not informed as to what is the cause of the differences be- 

 tween solar and culinary heat. 



17. It is evident, that the particles of all the three varieties of rays 

 are minute, to a degree beyond our powers of conception ; probably 

 they are equally minute, but of this we are not certain. 



18. It is evident, therefore that we cannot expect to ascertain the 

 weight of either of these kinds of rays ; as already remarked, our 

 organs, and our instruments are too coarse for such delicate trials. 



19. There is a great analogy between light and heat they agree 

 in nearly all their physical properties; but light produces vision and 

 colors caloric, expansion and heat. 



(a.) Light cannot be, at all, imprisoned. When the source from 

 which it flows is intercepted, except in the case of the solar phos- 



* Neither muriate of silver, nor a mixture of chlorine and hydrogen gases, was 

 affected by the concentrated light from the burning carburetted hydrogen gases ; 

 but the light from electrized charcoal speedily blackened the muriate, and exploded 

 the chlorine and hydrogen, or caused them to combine quietly. Grande. 



t The chemical effect probably follows the same law ; possibly also the magnetic. 



