18G FRAGMENTS OF SCIENCE. 



paper, two holes are pierced in it, corresponding to the 

 images of the two coal points : but falling on a thin plate 

 of carbon in vacuo, or upon a thin sheet of platinized plat 

 inum, either in vacuo or in air, radiant heat is converted 

 into light, and the image stamps itself in vivid incandes 

 cence upon both the carbon and the metal. Results similar to 

 those obtained with the electric light have also been obtained 

 with the invisible rays of the lime-light and of the sun. 



Before a Cambridge audience it is hardly necessary to 

 refer to the excellent researches of Professor Stokes at 

 the opposite end of the spectrum. The above results con 

 stitute a kind of complement to his discoveries. Professor 

 Stokes named the phenomena which he has discovered and 

 investigated Fluorescence ; for the new phenomena here 

 described I have proposed the term Calorescence. He, by 

 the interposition of a proper medium, so lowered the re- 

 frangibility of the ultra-violet rays of the spectrum as to 

 render them visible ; and here, by the interposition of the 

 platinum-foil, the refrangibility of the ultra-red rays is so 

 exalted as to render them visible. Looking through a 

 prism at the incandescent image of the carbon points, the 

 light of the image is decomposed, and a complete spectrum 

 obtained. The invisible rays of the electric light, remoulded 

 by the atoms of the platinum, shine thus visibly forth ; ultra- 

 red rays being converted into red, orange, yellow, green, 

 blue, indigo, and ultra-violet ones. Could we, moreover, 

 raise the original source of rays to a sufficiently high tem 

 perature, we might not only obtain from the dark rays of 

 such a source a single incandescent image, but from the 

 dark rays of this image we might obtain a second one, from 

 the dark rays of the second a third, and so on a series of 

 complete images and spectra being thus extracted from the 

 invisible emission of the primitive source. 1 



1 On investigating the calorescence produced by rays transmitted 

 through glasses of various colors, it was found that in the case of certain 



