280 Pearsall on the Communication of 



From the very feeble phosphorescent effects obtained by 

 exposing substances to the intense light of the discharge, and 

 also to the constant current of voltaic electricity, it is inferred 

 that light, and great quantity of electricity, are not essentially 

 necessary, but that the effects are due to electricity of great 

 intensity, and hence the influence of the discharges of ordinary 

 electricity. 



As electricity itself does not permeate glass, the effects upon 

 substances hermetically sealed up may be thus explained : 

 when the outsides of the glass tubes are electrified by the 

 intenseness of the discharge, a corresponding state is simul- 

 taneously induced upon the interior surface, and the con- 

 tiguous substances are rendered phosphorescent by the so 

 excited electricity. 



The colours of bodies, generally, are believed to be due to 

 peculiar structures capable of decomposing light, and reflecting 

 particular coloured rays. 



Since by experiment I have shown that colorific structure 

 obtains in certain varieties of colourless fluors, as the result of 

 intense electrization; and as electricity, under various con- 

 ditions, manifestly commands the relations of molecules and 

 masses of matter, by effecting, destroying, or suspending their 

 combinations, may it not be advanced, that when matter 

 (such as calcined fluor) which is not phosphorescent, is ex- 

 posed to electric discharges, that they cause vibrations of the 

 particles, which, being repeated with every discharge, gradually 

 modify the structure, and bring it into a peculiar state ? 

 May not the action of heat allow this state to return to what 

 it was originally ; and from the vibrations of the atoms of 

 matter in changes of structure proceed the undulations fitted 

 to produce light? 



This explanation appears to me to be in perfect conformity 

 with the received laws and actions of light, heat, and elec- 

 tricity ; and also with the conditions of the earthy substances. 



Other causes, competent to these alternating changes of 

 structure, may exist besides heat and electricity, but the above 

 view seems to apply to the phenomena of phosphorescence 

 generally. The alteration of phosphoric colours after some 

 time may be regarded as consequent to the variations of 

 atmospheric temperature having been sufficient so far to alter 



