Intelligence and Miscellaneous Articles. 395 



same appearances when submitted to the action of electric light. 

 Nor is this all ; if slightly excitable oyster-shells be placed at a di- 

 stance of several inches, the phosphorescence produced by the first 

 discharge is usually weak ; on the second discharge it is stronger, 

 and on continuing the discharges, the luminous property is still fur- 

 ther increased, and acquires a considerable degree of intensity. It 

 is therefore evident, that the direct electric light, acting at a distance, 

 predisposes the particles of the shells more and more to become phos- 

 phorescent. I ought not to omit to mention, that in these cases I 

 perceived a smell of sulphuretted hydrogen, derived from the action 

 of the sulphuret of calcium on the water contained in the air, and 

 that it became more sensible as the number of the discharges in- 

 creased, which seems to indicate that the tendency to decomposition 

 increases with the luminosity. 



These first observations being finished, and especially considering 

 the before-mentioned experiment, from which no inference had been 

 drawn, that is to say, that calcined shells inclosed in glass tubes and 

 exposed to electric discharges were only phosphorescent on account 

 of the increase of temperature, it occurred to me to try whether sub- 

 stances traversed by diaphragms would lose or preserve their property 

 of becoming phosphorescent at a distance. The substances which I 

 employed as screens were white glass, red glass coloured by pro- 

 toxide of copper, violet glass, and also of various other tints, glazed 

 paper and leaves of gelatin. I was perfectly aware, that except red 

 glass, the other coloured glasses would not admit of the passage of 

 simple rays, but I thought that these substances would nevertheless 

 suffice to aiford differences sufficiently marked, as to the mode in 

 which electric light, the subject of my inquiry, would act. 



The discharge from eighteen jars was passed through recently cal- 

 cined oyster- shells, contained in a capsule, at a distance of about 0*4 

 of an inch . The experiment was made in a dark chamber, in which 

 I had remained for a quarter of an hour, in order ro render the retina 

 sensible to feeble light, and my eyes remained closed after the dis- 

 charge, in order that the sight might not be impaired by the impression 

 of the electric light. The shells immediately appeared strongly illumi- 

 nated ; the experiment was repeated in ten minutes, a plate of glass 

 about 0*01 1 7 of an inch thick being placed upon the capsule. The dis- 

 charge again produced phosphorescence, but in an infinitely less 

 degree than before the interjjosition of the screen. On increasing 

 the thickness of the glass to about 0'0315 inch, the phosphorescence 

 was still weaker, although the glass was perfectly diaphanous. This 

 experiment repeated at a distance of about four and even at eight 

 inches, still produced phosphorescence, but in a smaller degree. A 

 plate of glass about 0'04 of an inch thick, also gave very weak phos- 

 phorescence, and so also did a sheet of very transparent glazed paper 

 of \ the thickness of the glass. 



We have here, therefore, very diaphanous bodies, which allow of the 

 greater part of the luminous rays to pass, and whicli take away from 

 these same rays the property by which they render bodies phospho- 

 rescent. 



