376 



ON METALLIC PHOSPHURETS. 



comes solid, and assumes the colour and transparency of 

 the finest amber*. 



§ 13. I cannot conclude this paper v;ithout mentioning 

 some experiments I undertook, during my residence atRome, 

 on a species of glow-worm, the lampyris italica Lin., pro- 

 digious numbers of which are found in the summer in all 

 parts of Italy. 

 Experiments '^'^^ ^'S^* "^ *^^^ insect continues some time, ivhcn it is 

 on the light of kept under water. It does not appear to be diminished for 

 elow-worm ^^^ ^''^^ quarter of an hour, and is some hours before it 

 ceases entirely. If oil be used instead of water, it is ex- 

 tinguished more speedily, the light ceasing in fifteen or 

 twenty minutes. It is extinguished equally in hidrogen gas, 

 carbonic acid gas, and in nitrous gas extricated in the hy- 

 dropneumatic apparatus. If the insect be withdrawn from 

 these gasses soca after its light is extinguished, its phospho., 

 rescence revives by the mere contact of the air; but when it 

 will not revive even in oxigen gas, there is a mode of re- 

 producing it with peculiar lustre. This consists in placing 

 the insect, whether living or dead, in the rntilant fumes that 

 arise from the mouth of a phial filled with nitrous acid. As 

 soon as these vapours touch the abdomen of the insect, this 

 becomes luminous, and diffuses a greenish phosphorescence, 

 which speedily increases, till it becomes of a dazzling bright. 

 , ness ; and afterward diminishes in proportion as it increased, 



till it entirely ceases. This beautiful phenomenon conti- 

 nues about a minute only ; and though I have tried various 

 means, I could never revive the phosphorescence after its ex- 

 tinction in nitrous vapour. If oxigen gas, or even atmo- 

 spheric air, be passed up into a phial containing the insect 

 and nitrous gas, the light will soon reappear with more vi. 

 vidness than in its natural state. 



Fulminating 

 lead. 



P.S. After this paper was sent to the editors of the An- 

 nales de Chimie, I found a new property in the phosphuret 

 of oxide of lead, which I had not observed before. Having 



* I have noticed this phenomenon with soda in particular, and 

 I had added gradually a larger proportion "of this alkali than that I 

 have mentioned of potash, § 4. 



slijgh t\y 



