of Light ; and a new Theory of Fision. 41§ 



1! a substance adliering to water and glass—- and, by analogy, to 

 every other medium possessing these properties — that does reflect 

 light, because it may be removed ; and when it is, the surfaces of 

 these bodies no longer do reflect any I'ght ; and lastly, by that 

 part of the atmcsphere of Saturn which reflects the light, usually 

 denominated his ring ; for it is evidently not his atmosphere that 

 reflects this light, or the whole of it would be equally illumi- 

 nated; and as it is contrary to all analogy to suppose that any 

 thing could reside on the surface of air lut what is lighter than 

 air, the substance that reflects this light can be no other than 

 some buch a delicate fluid as I have supposed reflects the light 

 from the surfaces of glass and water, and if it is true in one in- 

 stance it may be in another. 



1. The cause of the reflection of light* must be attributed 

 either to the resistance of a substance that opposes its admission, 

 or to the dislike of the rays to enter a medium where that sub- 

 stance resides. Now if this objectionable substance made a part 

 of the glass, it is evident that the same substance would be found 

 in equal proportions all through, and the rays would be reflected 

 from the interior as well as from the surfaces, which is contrary 

 to fact ; but very few wo-.ild, in that case, be able to get through 

 to the other side, and glass in consequence would reflect a mass 

 of light, as it does now when pounded into dust, but no distinct 

 image of any object, and could be only a semi-transparent body, 

 instead of a clear pellucid substance as it now is. 



If it be said that glass, in consequence of some sort of chemi- 

 cal process, by the contact of the air might possess this property 

 only on its surface, I ""swer, that this is not sufficient to account 

 for the phaenomenoi , because, as glass reflects light ifiwardly 

 from its further surface, that part of the surface that did so would 

 be inside, and could not be in contact with the air ; and there- 

 fore, if it were the particles of glass that reflected the rays back 

 again, all the particles throughout would also reflect light, 

 for they all have the same nature ; and consequently we can only 

 get rid of the difficulty by supposing that it is not the glass, 

 but a fluid that adheres to it, that has the property of reflecting 

 light. 



2. I am now to show that there is b substance adhering to 

 the surfaces of water and glass which may be removed, and that 

 no light is reflected from those parts of the surfaces of these 

 bodies from whence it is removed. 



In the Enctjclnpcpdia Brliannica, under the article Optics, 



• I have separatefl these two phimomcna, and begin with reflection in 

 order to avoid confubioii : when the cause of this is fully comprehended, 

 tilt cuuiic of the refraction of light will be very easily understood. 



I» p 2 a"d 



