272 Pearsall on the Communication of 



N After 21 days in After 21 days in Portions kept in the dark 



Light. Darkness. for three months, 



10. No light Green and purple light . . j 



11. Very feeble on I ... v 



some portions l Cha . n S m S ^ nis ' ending! 

 only *! 



12. Faint light ..... ^^' eo f *} Yellow ^i purple light. 



Dark green and \Brighter green, remained with Apatite, which also has been 

 yellow tints . . . / calcined and electrified. 



It appeared that during twenty-one days' exposure to sun- 

 light, that the portions of Nos. 1, 5, 11, and 12, lost nearly all, 

 and Nos. 9 and 10 all their phosphorescence ; also, that 

 Nos. 1, 4, 6, 7, 8, and 12, had the colours modified during the 

 time of exposure, as compared with their phosphorescence given 

 in Table 1 : orange and purple tints seem to be assumed by time. 



The third column gives the phosphorescence conferred by 

 electricity, which remained after an interval of nearly three 

 months. 



The effects detailed in this and in my previous communi- 

 cation are those produced after the destruction of the phospho- 

 rescence, which naturally existed in the minerals, by the appli- 

 cation of a strong heat : another class of effects are now to be 

 introduced, resulting from the electrization of bodies still retain- 

 ing their native phosphorescence. 



The result of this obvious extension of the inquiry was a 

 series of magnificent colours, and an exaltation of the original 

 phosphorescence, of which it is very difficult to convey an idea. 



Crystals of the FLUORS, whose localities are given in Table 1. 

 (p. 269), were used in the following experiments, upon the induc- 

 tion of additional phosphorescence by electricity. The same 

 order of the substances is preserved in the present table. 



No. of Heated to decrepitation colour 

 Minerals. Colour of Natural Electrical of superinduced Phosphoric 



Phosphorescence. Discharges. Light. 



1. Green fluor. ~| (Green, bright blue, intense rich 



Yellow green \Pink and orange.. 24 \ purple, with after tints of pink; 

 portion . . . J [ very strong light. 



Bluish green j 1 ^' nearly white, 1 , yi id emcrald reen then ur _ 



f Intense purple, several portions 

 gave deep orange light : after 



2. Green fluor...( CoW V, M M aml l 20 \ it had been heated to redness 

 purple light.... J j for some timej it was stm 



luminous with a bluish light. 



