On the Refraction of Light. 367 



the solar light entering a dark chamber, I fixed the lens thus adjust- 

 ed in the isolated red rays, which were refracted in their passage 

 through the lens, and made to converge to a focal point at precisely 

 twenty four inches from the glass. The lens was then fixed in the 

 violet rays, which having passed through it, converged to a focus at 

 exactly twenty four inches from it. The orange, yellow, green, 

 blue, and indigo rays were passed separately through the lens, and 

 all made to converge to one focus. A bi-convex glass, whose focal 

 distance is four feet, was subsequently employed, and gave results 

 scrupulously analogous to those already stated : all the differently 

 colored rays converging at the same distance from the lens. 



Double concave glasses were used to determine whether the di- 

 vergent rays of the different colors would form circles of equal diam- 

 eters, at the same distance from the lens. The circumference of 

 the circle formed by the divergency of the red rays was accurately 

 marked with a pencil on letter paper, and the circle produced by the 

 violet rays was found to have, at an equal distance, the same diame- 

 ter. These experiments are obvious and simple, and they go to es- 

 tablish that the rays of all colors are equally refrangible. 



If we admit that the several colorific rays are endowed with dif- 

 ferent degrees of refrangibility, we must be prepared to admit the 

 following results, as the necessary consequence of such a property. 



1. A beam of white light, in passing through a diaphanous medi- 

 um of equal thickness, as a plate of glass, with parallel surfaces, 

 would undergo analysis, and the colors would appear in the order of 

 their refrangibilities. 



2. Bodies viewed through different colors of light would appear 

 of different magnitudes ; for the focal distance of the crystalline lens 

 would vary, according to the refrangibility of the rays. 



3. A double convex glass would have seven foci ; for the violet 

 rays, being most refrangible, would converge soonest to a focus, and 

 the red rays, being least so, would form the most distant one. If, 

 therefore, the violet focus were received on paper, it would be seen 

 surrounded with six circles of colored light, of which the red would 

 form the external. 



4. The same chromatic circles would appear, if solar light were 

 transmitted through a double concave glass ; with this difference, that 

 in the latter case, the center would be formed of the least refrangible 

 or red ray, and the circumference of the violet. 



Vol. XX.— No. 2. 46 



