270 Pearsall on the Communication of 



8. Partofthecrystal-1 



lized surface of ITT- i j. i L- 



dark fluor formed I Violet, changing to jfi*f 12. Light of short duration 



in radiated concre- 1 and blue * 60 ' Strong light, nearly white. 



tions (Derbyshire)] 



Other Examples of Fluor s may be added. 



9. Cubic fluor,transpa-l R . , ( 12. No light. 



rent violet crystals f ' \ 24. Faint purple light. 



{12. Faint blue and pink, chang- 

 ing to yellowish light ; strong 

 light towards the close. 



11. Green fluor fftolet, pale yellow, pinkUZ. Bright green, changing to 



' ' \ and pale blue tints . . . j purple, good light. 



12. White portion, from |p , (12. Violet, changing to steady 

 massive purple fluor J u P e j lemon-coloured light. 



On comparing the native phosphorescence with that induced 

 by electricity in the same substance, the series of colours 

 appeared to differ in nearly every specimen subjected to ex- 

 periment. While some of the natural fluors can exhibit light 

 of different colours, only a single colour may be conferred by 

 electric action ; or, on the contrary, a coloured light, naturally 

 held, may be replaced by a variegated phosphorescence, in 

 which the original tint dbes not appear. 



As the communicated light, in many specimens, obviously 

 increased in variety, beauty, and intensity of tints, when sub- 

 jected to repeated electrical explosions, the following experi- 

 ments were made to observe the progression of this property. 

 The green fluor, from Wear-dale, Cumberland, No. 2 of the 

 preceding table, was selected on account of the deep colour of 

 the light given to it. After calcination it was placed in the 

 influence of the following explosions, which were regulated by 

 a discharging electrometer attached to the jar. 



The variety of fluor was naturally phosphorescent, with deep 

 blue and purple light, and the following experiments were 

 made upon the same portions : 



1st Discharge faint purple phosphorescence when heated. 

 2nd faint green, succeeded by purple. 



3rd the same colours strengthened, and extended in duration. 



4th the purple increased. 



6th green light is brighter and stronger. 



10th strong green light, the purple rich, and increased in duration. 



