10 



sage near the edges of bodies, whether opake or transpa- 

 rent, they are diverted from the right lines, and reflected 

 towards those bodies. This action of bodies on light 

 exerts itself, at some distance, but increases as the dis- 

 tai.re is diminished, as appears in the passage of a ray 

 between the edges of two thin plates, at different aper- 

 tures, in which it is peculiar, that the attraction of one 

 edge is increased as the other is brought nearer it. The 

 rays of light passing out of glass into a vacuum, are not 

 only inflected toward the glass ; but if they fall too ob- 

 liquely, they will revert back to the glass, and be to- 

 tally reflected : this reflection cannot be owing to any 

 resistance of the vacuum, but merely as the attracting 

 power of the glass. This appears farther from hence : 

 if you wet the posterior surface of the glass, the rays, 

 which would otherwise have been reflected, will pass 

 into and through that liquor: which shews that the rays 

 are not reflected, till they come to that posterior sur- 

 face of the glass, nor even till they begin to go out of it ; 

 for if at their going out they fall into any liquor, they 

 sre not reflected, but persist in their course, the attrac- 

 tion of the liquor counterbalancing that of the glass. 



From tiiis mutual attraction between the particles of 

 light and other bodies, arises the reflection and refraction 

 of light. The determination of any moving body is 

 changed, by the interposal of another body. Thus 

 light, meeting any solid body, is turned out of its way 

 and reflected : but with this peculiar circumstance- 

 it is not reflected from the body itself, but by something 

 diffused over the surface of that body hefore^it touches 

 it : it is the same thing in refraction. The rays refracted 

 come very near the refracting body, yet do not touch it. 

 Those that actually touch solid bodies, adhere to them, 

 aiid are as it were extinguished and lost. 



This entirely agrees with the curious observation of 

 an ingenious writer. " It is common to admire the 

 lustre of the drops of rain, that lie on the leaves of 

 coleworts and some other vegetables. Upon inspecting 

 them narrowly I find the lustre rises x from a copious 



