276 Pearsall on the Communication of 



tubes, with the view of deducing, if possible, the proportion of 

 effect due to radiant matter passing off from the sparks : I found 

 that phosphorescence was effected, although glass intervened, 

 as the following facts will prove. 



1. Portions of calcined scollop and oyster-shells were her- 

 metically sealed up in small glass tubes placed within a longer 

 tube, and the electric discharge effected its passage over the 

 outsides of these little tubes. 



After one hundred and sixty discharges of a jar, these sub- 

 stances were found, when heated, to be phosphorescent. 



2. Six small tubes, sealed at both extremities, containing 

 calcined chlorophane, calcined cuttle-fish bone, and calcined 

 scollop-shells, were introduced into a glass cylinder, open at 

 both ends : large shot were rolled in to keep the small tubes 

 together, and to conduct the electricity. 



This glass cylinder was then introduced into a glass tube of 

 larger diameter, the space between being filled with portions 

 of calcined oyster-shells and different fluors ; the glass cylinders 

 were placed horizontally. 



Two hundred and twenty-five discharges of ajar were then 

 made through the inner tube ; the fragments contained be- 

 tween the two cylinders were decidedly phosphorescent when 

 heated. 



The tubes which had been thus strongly electrified had their 

 contents examined. 



The chlorophane fluor in two tubes was not phosphorescent. 



The calcined oyster-shells had acquired an orancje-pink and 

 bluish light. 



Other two tubes had calcined scollop-shells, which instantly 

 gave, when heated, a flame-coloured phosphorescence, with pink 

 and purple colours. 



These experiments were necessarily very laborious ; fewer 

 explosions produced degrees of the effects ; but I did not feel 

 satisfied with giving the less decided results of thirty or forty 

 explosions. The two experiments, given above, required about 

 3000 revolutions of a large cylinder machine in good action. 



I then resorted to voltaic electricity, as a source of phos- 

 phorescent power, although, at first, any effect might be sup- 

 posed to be precluded, either by the insulating power of the 

 mineral, or when the quantity and the intensity of the electricity 



