186 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 



