Phosphorescence and Colour by Electricity. 279 



The blue tints are strongest upon the angles of the frag- 

 ments, and upon the solid angles of the fissures. 



And I may call attention to a similar distribution of colours 

 to be observed in large crystals and specimens of massive 

 dark purple fluor, which have their colours unequally con- 

 ferred upon the surface, some portions being nearly white, 

 other parts having faint tints of violet, purple, or blue ; while 

 towards the edges and solid angles of the crystals, the colours 

 increase to intensity. 



If massive dark fluor be broken into fragments, some of 

 those may be selected which are scarcely tinted, except upon 

 the edges and surfaces of the differently crystallized portions 

 just separated, and upon these parts intense colour resides. 



I took a large mass of purple fluor, weighing several pounds, 

 and a portion was broken from a large cubic crystal, which 

 was deep purple in the solid edges and angles, while the 

 internal part near to the centre of the external planes was 

 nearly white, the crystals having a mottled appearance ; the 

 white portion was highly phosphorescent : calcined in a crucible 

 to redness, and subjected to electricity, no colour was pro- 

 duced, although it became highly phosphorescent. 



Fluor spars with different colours were electrified in their 

 natural state, but no alteration or addition of colour was 

 remarked, excepting the dark purple fluor, whose depth of 

 tint was increased. 



It is a curious circumstance, that those portions of fluor 

 which are naturally the most coloured, are also, when ren- 

 dered white by heat, recoloured with the greatest facility by 

 electricity; and as the latter power would appear to confer 

 colour only by modifying in some way the arrangement of the 

 particles, may not natural fluors owe their colours to structure? 

 And may we not be allowed to suppose that nature used the 

 same means, and that ELECTRICITY confers colour and phos- 

 phorescence in the first instance ? Both the natural and the 

 induced colours are destroyed by heat ; and the colour, like 

 the phosphorescence, may be repeatedly restored by electricity. 



I may now, perhaps, venture to draw the following con- 

 clusions from the experimental details advanced, which have 

 proved electricity to be efficient in the restoration of phospho- 

 rescence. 



