PRODUCED BY ELECTRO-CHEMICAL ACTIOX. 97 



by Newton around the point of contact of two slightly convex glasses or 

 lenses. The order of the latter colours should therefore correspond ex- 

 actly with that of my scale. It does so in fact; but that the correspond- 

 ence may be perceived, it will be necessary first to rectify some errors 

 which have arisen respecting the rings of Newton, either in consequence 

 of their small dimensions, or of their having been examined under the 

 influence of some prejudice. 



Our scale embraces the extent of the first four rings, and consists, as 

 we have already stated, of foi-ty-four tints. 



The tints of No. 1 to No. 10 (inclusive) correspond to the 1st rinff. 



11 28 2nd_ 



29 38 3rd_ 



39 44—— _4th — 



Fundamental Principle. 

 It is well known that the colours of the thin layers around the point 

 of contact of Newton's glasses are formed in the following manner. At 

 the point which allows all the rays of the transmitted light to pass there 

 appears a dark speck, and this remains the same whatever may be the 

 quality of the light. If the incident light is white, the central speck is 

 succeeded by several irises or concentric rings. If the light is homo- 

 geneous or produced by one species of rays, the irises are changed into 

 rings of the same colour as the incident rays, and separated from each 

 other by dark intervals. These rings, whatever be their colour, have 

 their commencement all at the verge of the central speck, but they oc- 

 cupy diflferent spaces. The violet rings are the narrowest and nearest ; 

 the red are the widest and most distant; the rings of the intermediate co- 

 lours are of intermediate dimensions andat intermediate distances. When 

 the incident light is white, the series of homogeneous rings are formed 

 simultaneously and overlap each other ; all the colours are intermixed in 

 different proportions, and none stands isolated. It is to these combina- 

 tions that we are to attribute the tints of the thin layers which we are 

 about to analyse on our scale. 



First Ring.— From No. 1 to No. 10 (inclusive). 

 The Scale commences with the blond* colour: of this there are four 

 gradations, the first of which is silvery, and 2, 3, 4 are gradually deeper. 

 The blond is succeeded by the tawnyf . Of this there are three species, 



• [The term blond employed in the original has been retained in the trans- 

 lation to avoid the difficulty of giving an exact equivalent. Those brownish tints 

 which m reference to human hair we term light or fair are evidently intended 

 — Edit.] ' 



+ [In the original the name of this colour is fauve, from the Latin /«/i')« ; and 

 the author says that he employs it in order to avoid the circumlocution of 'lion- 

 colour'. — Edit.] 



Vol. I — Part I. ii 



