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stitial substance throughout which they are diffused. 

 The fact of the gradual and not instantaneous evolu- 

 tion of the light, and the slow eclipse it suffers, seems 

 to refer the phenomenon to the volition of the insect 

 the intervention of a shade or contraction of the fibres to 

 which the luminous points are appended, would account 

 for the occasional occultation of the light. The lumin- 

 ous matter heated in a platinum spoon soon ceased to 

 evolve light : the surface of the platinum exhibited no 

 change, which it would have done had the luminous 

 matter contained phosphorus as one of its chemical 

 constituents. The light of the glow-worm seems 

 monochromatic, and appears incapable of further de- 

 composition by the prism. Viewed through a prism 

 of rock crystal turned on its axis, it presented a con- 

 fused nebulous image, unaccompanied with any chro- 

 matic tint. The photometer was affected by 2 or 3 

 on its near approach : this could only be inferred from 

 the apparent sinking of the liquid, calculating from 

 the moment of observation to that when it became 

 stationary. The luminous spherulae secreted from the 

 insect, when dry, were heated over a spirit lamp in 

 a platinum spoon : they became dark brown, and ex- 

 hibited a momentary flame, accompanied by slight 

 explosion, the flame, in colour, &c. had all the charac- 

 ters of hydrocarbonate ; and, by a delicate chemical 

 analysis, we have inferred it to be a gummo-albuminous 

 substance. Luminous spherulse detached from the 

 glow-worm were immersed in various media to ascer- 

 tain the period of continued luminosity. In a con- 

 centrated solution of pure caustic potassa, the light 

 was of a bluish tint, and seemed to undulate : the 

 period of duration was 60 seconds, and it continued 

 luminous for several minutes in tincture of iodine. In 

 sulphuric acid, of specific gravity 1.85, it was luminous 



