Phosphorescence and Colour by Electricity. 273 



No. of Heated to decrepitation colour 

 Minerals. Colour of Natural Electrical of superinduced Phosphoric 



Phosphorescence. Discharges. Light. 



, 7 ,. ...... ., ,. ( Lemon-yellow, violet, and seve- 



3. Yellow fluor.. rather l 16 { ral colours changing during 



[ decrepitation. 



. bl 



4. Light 

 fluor 



greenfPale green, 

 . 8 . .. an 



6. Dark purple ( Green, pink, purple, ) 

 fluor ...... 1 and orange ..... J 



7. Dark fluor 



~ . , , . , 



{ tints } 



* IH S .......... ^ 



8. Dark fluor 



Faint 



and l 

 J 



9. Cuhic 

 fluor 



violet 



16 



29 



14 



12 



10 



\ Green 

 { 



^raw-yellow purple, 

 and several other 



f Dark green, lemon- yellow, pur- 

 ple, and orange; the light 

 j from some portions was very 

 I strong, and nearly white. 



{Peculiar intense light of straw 

 whiteness, then greenish, dull 

 orange, and pink tints. 



11 rrPPnflnnr 

 01 



and omn^e- ) 

 ye//ow; ......... / 



Compact darkly d 



purple fluor . J 



Apatite ( phos- ( Brilliant yellow- 

 phate of lime)\ yree/ ......... 



\ pink, and orange colours. 

 ("Intense azure-blue, (some yel- 

 \ low,) very vivid light nearly 



I white, from points of the 

 fragments. 



( Brilliant emerald-green, violet 

 I and orange, very strong light, 

 j finally faint purple ; these were 

 I striking changes. 



12 



f Green yeltow, pink, and orange 

 \ light. 



( Green, yellower, olive and orange 

 I tints, very strong light. 



The additional phosphorescence appears to differ in colour 

 from the natural quality, and to be evolved at a lower tempera- 

 ture, and blends into the previous natural phosphorescence, 

 which also is increased in strength and duration. 



These experiments may suffice to show that minerals, which 

 naturally are phosphorescent when heated, do not necessarily 

 exhibit the maximum degree of this peculiarity, but may have 

 it exalted by artificial means. The phenomena are so far 

 increased, that specimens of fluor, which held dull or unde- 

 fined phosphorescence, have been rendered, by electricity, 

 equal to the most eminent class of phosphorescent fluors; 

 some varieties, indeed, rivalling the intensity of chlorophane, 

 or Siberian fluor. The means of increasing the natural phos- 

 phorescence in bodies has not, as far as I know, been here- 

 tofore pointed out. 



Portions of these electrified minerals were kept in darkness, 



