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| F ~ Sa ss gies eh f ae as” , 
356 | “On the Refraction of Light ee 
lead, pierced with holes of nearly a hiietin diameter, at — distan- 
_ces from one another, (about an inch,) and in the same line. The 
bases of the pyramids, formed by the insulated colors, being received 
on paper, were found to occupy exactly the same spaces, and to 
equal to one another.* ‘The rays of the pers colors are, there- 
fore, all equally diffrangible. a4 
The s of bodies in tomaogencall ht 
_ fringed with colors, as in compound light, are bordered by concen- 
“trations of the color in which they are placed; > ane the luminous i 
streak around the border appears to be even more : distinctly devel- 
— in monochromatic than in white light. 
- Having always entertained some doubts about the diferent a 
gibilities of the colorific rays, notwithstanding the high philoso 
authority from which the theory emanated, I instituted a few. obvious 
experiments for the purpose of settling my mind on the subject. 
Before stating them, I beg leave to make a few introductory remarks. 
It is established that when the solar rays are transmitted through 
double convex lens, to a focal. point, their convergency is caused by 
the refraction which the rays undergo in the glass; ‘and hence it ne- 
cessarily follows that the distance of the focus from the lens is ¢s 
versely as the degree. of refrangibility possessed. by the light. 
MY other words, if light were more refrangible than it really is, its = 
would converge sooner to a focal point than they do, the same lens 
being employed. . Now according to the Newtonian doctrine, there 
is a gradation of refrangibilities fram the red to the violet rays; the 
rays of the latter being most refrangible, those of the former being 
_least so, and the Colors included between these extremes, possessing 
ediate degrees of refrangibility. ~Tt naturally follows that when 
the same double convex glass is used, the. point of convergency OF 
focus will be nearest the lens in the violet rays, less near to it in the 
indigo, still less so in the blue, and so on to the red rays, Be, which 
the ¢ glass must be greatest, si ithe 
possess less refrangibility than any of tlie other rays. Imp 
with these views, I obtained a double convex lens whose focal dis- 
tance in the compound solar light was two feet, and mounted it,on 4 
Sliding stick, accurately graduated. Having decomposed, bya prem 
mal Pe ee 
* The bases formed by the superior yellow rays and the nine ste am 
when viewed a distance, to be larger than the rest, but this een. 
greater power, by which they illustrate a space contiguons to - 
7 af ex 4 
, instead. of being 5 
