31$ APPENDIX. 



than water when it is poured on vitriolic acid* 

 But if we place water j which is perfectly transpa- 

 rent, in the focus, no heat will be produced : nay, 

 if spirits of wine were placed in the focus, they 

 would scarcely be heaied. But the same Heat 

 which melts iron, would more than suffice to make 

 water boil. From this experiment, then, without 

 advancing farther arguments, it appears that the 

 rays in themselves have no Heat ; and there is no 

 reason to suppose that the sun is hotter than the 

 earth we inhabit. 



It is a question that has been much agitated, 

 whether the solar rays be matter, or only an ar- 

 rangement of matter; but their materiality is now 

 pretty generally admitted: but a question which 

 has not yet been answered satisfactorily, is, " If 

 f* Light be matter, what becomes of it ? " Perhaps 

 there is a distinction between Light and the solar 

 rays, which has not yet been properly attended to. 

 The sun's rays heat bodies only when they are 

 lent or destroyed. (The term absorbed doesnot in 

 our opinion exactly answer the purpose.) Hence 

 they do not heat water if perfectly transparent ; 

 neither do they heat the air above the clouds: at 

 least, as very little bending takes place in these 

 cases, the heat is so trifling as to be scarcely worth 

 mentioning. The upper regions of the air, then, 

 are extremely cold, though exposed to the direct 

 action of the sun. 



When a ray of Light is reflected, it does not 

 touch the body reflecting it; but is thrown back 

 before it arrives at the surface : therefore the more 



white 



