On the general Nature of Light. 163 



cum fiances feldom do lb fully concur. In moft cafes of the 

 reflexion of light, there is a portion of the falling light either 

 tranfmitted or abforbed. 



9. Light is abforbed in the bodies on which it falls, when 

 their attractions fix it in new compounds with their .arts; 

 or when they prefent a medium in which it may be for a 

 time lufpended, though not carried into actual combi- 

 nation. 



10. As the primitive colour of light depends, in a great 

 meafure, on the conformation and the relative arrangement 

 of its particles, fo the other colours which it affumes in re- 



ion depend likewifc on changes in' the arrangement of 

 thole particles which vary the effect of their conformation. 

 While the particles remain in the fame arrangement the 

 colour is the fame; and their elementary conformation, and 

 the law of movement to which thev are lubject, continue 

 their illuminating effect: to the eye till they are loft by ex- 

 treme diffusion, bv abforption, or perhaps by entire decom- 

 pofition. 



The permanent colours of the furfaces of bodies depend 

 on the fame laws as the colours of the rays of light. The 

 conformation and the arrangement of the extreme elementary 

 particles at the furfaces of all bodies determine, reflectively, 

 their different colours. White furfaces, for inftance, have 

 one conformation and arrangement of the minuted par- 

 ticles aL their extremities : blue furfaces have another con- 

 formation and arrangement of the fame particles : red fur- 

 faces another, &e. occ. Thefe extreme particles of the fur- 

 faces of bodies do not conftitute light, becaufe they are not 

 unconfmed and in motion, have not its peculiar rectilinear 

 elasticity, poffefs not its chemical affinities; but when 

 light is thrown upon them, they become vifible, eac!' fet of 

 particles under a different colour, jult as its conformation 

 and arrangement arc different. The extreme particles of 

 furfaces have the fame conformation and arrangement 

 • particles of light in a blue ray; and fo of other co- 

 lours. 



Y 2 XII. Ac- 



