18 



DECOMPOSITION OF LIGHT. 



salts. 



of this substance covering crystals of a calcareous spar, a» 

 well as the levigated calamine of the shops, were phospho- 

 rescent. 



Muriate of antimony is not luminous. 



Phosphate of lime and antimony, or James's powder of 

 the apothecaries is very phosphorescent, its light continu- 

 ing for some minutes. 



Tartrite of potash and antimony, or emetic tartar of the 

 apothecaries, is luminous, but not comparable with James's 

 powder. 



Miscellaneous Sabstances. 

 Compounds Soaps. — Common hard white and brown soaps afford very 



containing good sparks, which are sometimes flame-coloured on the 

 surface; but they are not luminous even in the track of the 

 fluid upon their surfaces. Neither is the common soft soap 

 at all luminous. 



Sulphuret of potash gives a purple hissing stream, and is 

 not luminous, in which it totally differs from the sulphuret 

 of lime. 



Common fulminating powder is not luminous, neither 

 does it explode with the shock which I employ in these ex- 

 periments. 



Gun powder is not rendered luminous by the electric 

 light, nor does explode with a small shock. 



In my first letter correct — Vol. XV. p. 281, 1. 7 from 

 bottom, after surface, insert and lastly along its surface. — 

 P. 282, 1. 3. from bottom, for sulphate r. sulphuret. 



On the Decomposition of Light into its most simple Elements; 

 a Fragment of a Work on Colours: by C. A. Prieur, 

 formerly Colonel in the Corps of Engineers, and Lec- 

 turer in the National Institution.* 



White tight <\e- W HITE light is decomposed by refraction into an infi- 

 diffcrent Co- ° llltc mimD8r °f parts or rays. They have a different co- 

 lours, 



* * Abridged from "the Annaks de Chimie for Sept. 1806, p. 227. 



lour 



