180 New Publication. 



The object of the prefent treaiife is to explain, in a man- 

 ner confident with the leading principle formerly advanced 

 by the author, another important clafs of the phamomena of 

 light and colours. 



Sir If.iac Newton has reprefented the fmalleft parts of all 

 natural bodies as tranfparent. He fuppofcs thofe parts to be 

 placed in a medium, inferior in refractive power to them- 

 felves Thofe bodies are in his estimation tranfparent, which 

 con hit uniformly of the fmalleft parts and the fmalleft inter- 

 mediate fpaqes.; thofe are black, which have their integrant 

 parts and the intervening fpaces of a fize fomewhat greater: 

 fuch as are varioufly coloured confift of parts larger than 

 thofe of either tranfparent or black bodies. The rays of 

 light are, in his judgment, ciifpofed, by a natural indeftruc- 

 tible quality, to be alternately tranfmittcd through oppofing 

 media, and reflected from them. By this quality, the tranf- 

 miflions of light, its refractions and its reflections, appeared 

 to him to be in all cafes regulated. 



The author of this treatife, on the contrary, denies that 

 the minuted integrant particles of bodies are known to be 

 tranfparent; that there exift within bodies any fuch refrac- 

 tive media furroimdiug their parts as Newton has imagined j 

 that refraction and reflection depend in any meafure on the 

 arrangement and conformation of the parts of bodies, which 

 Newton fuppofcs ; or that light is, by a mvfterious natural 

 quality, difpofed, by turns, to eafy tranfmifhon and to eafv 

 reflection. 



tie maintains, that all the phoenomena which Newton has 

 thus erroneoufly explained, are only fo many different cafes 

 of the inflection of the particles of light by the attractions of 

 bodies approaching them. According to him, as it mould 

 feeni, light is never, in any ctrcuniftances, made to exhibit 

 a diyerfity of colours in its rays, otherwife than by the points 

 or edges of approaching bodies exerting on it an attractive 

 force fufficicnt to deftroy the natural confiftency of the whole, 

 or at leaft a part, of the white ray. Refraction and reflection 

 depend upon no peculiar qualities in light, but (imply on the 

 attraction exefclfed upon it, according to the general laius, by 

 the other bodies with which, in various circumftances, it 



comes 



