282 ELECTRIC LIGHT. 



Calcareous less phosphorescent, and the sparks taken along the snr- 



spars very lu- face of a piecc of rhombic spar was reflected so intensely 



minous by the -.,,.,,, . , ,, . , ,. 



electric shock *^ *^ illuminate the whole table with a brilliant white 



'light. 

 "7 ?f'^^^'^*^^y Amongst the aerated species, common chalk was ex- 

 tremely lum?noiis when the shock was passed at some 

 distance above it, and when passed along its surface the 

 fluid left a very vivid zig-zag track of light, which con- 

 tinued for spveral minutes. 

 Ketton stone. Next to chalk in its phosphoric appearances was a 

 i stone called Ketton stone, which consists of large distinct 



grains, aggluted together like the roes of fish ; in passing 

 the shock along its surface, some portion of the stone was 

 shattered, and its iumiuous grains dispersed in all di- 

 rections. 

 Other bodies. Amongst the several varieties of the sulphate of lime, 

 the specular gypsum, or selenite, is by far the most beau- 

 tifully phosphoric, but at the same time its light is much 

 inore" evanescent than in other substances which are less 

 luminous. An oblong six-sided prism of specular sele- 

 nite shone by the electric explosion with a vivid greenish 

 light, but it continued a very few seconds only. Nitrate 

 of linic fresh made, and tried whilst yet warm, gave small 

 jparks, which upon the surface of the nitrate were quite 

 red, or rather llame-colourcd, and it absorbed the elec- 

 tric light but slightly. Muriate of lime was somewhat 

 more phosphorescent than the nitrate. All the fluates 

 absorbed the light freely; the dark purple fluor spars 

 alforded no spark, but allowed the electric liuid to pass 

 in a purple stream, accompanied with a whizzing noise, 

 whilst a yellowish ilnor, and another with a greenish tint, 

 which was phosphoric by heat, afforded very good 

 sparks. 

 Sulphuret of Sulphuret of lime, commonly called Canton's phosphq- 

 Itmc partfca- ms, is much the most luminous by the electric explosion 

 ar y uminoub. ^^ ^^^ substance I have hitherto tried, and affords some 

 beautiful experiments, one of which I cannot help 

 mentioning. 

 Striking and Mix sulphate of lime with the white of an eg^, and 



beautitul expe- spread it about the tenth of an inch thick upon a piece of 

 board ; dry it in the air for a day or two (as it dries very 



slow). 



