. w >14 Mr. G. T. Deilby. Phosphorescence caused !>// [Fob. 9, 



the /3 rays, it showed no secondary phosphorescence on removal from 

 the cell, and no revived phosphorescence when it was heated to about 

 200. A brown coloration, which had resulted from the action of 

 the rays, had completely disappeared after the heating to 200. 

 After a further exposure of 48 hours to the /5 rays, the brown colora- 

 tion was much stronger, but it showed neither secondary nor revived 

 phosphorescence. 



31. A crystal of potassium iodide placed on the radium cell 

 phosphoresced faintly. After three hours' exposure the phosphores- 

 cence was distinctly stronger, and on removal from the rays a faint 

 secondary phosphorescence could be detected. This died out in a 

 few minutes, but was revived for a few minutes on heating the crystal 

 to 150. After 12 hours' exposure to the rays, a faint blue-green 

 colour had developed, which, however, disappeared after the crystal 

 had been kept in the dark for a few hours. 



32. A crystal of potassium chloride became red-purple after it had 

 been two hours on the radium cell; during the exposure it 

 phosphoresced faintly. On removal from the rays it gave a faint 

 and brief secondary phosphorescence and a brighter revived phos- 

 phorescence on heating to 100. After heating, the purple colour had 

 disappeared. 



33. A crystal of potassium bromide, after exposure for one hour, 

 became blue-green and phosphoresced brightly. On removal from 

 the rays it phosphoresced strongly, and on heating to 100, it glowed 

 with revived phosphorescence and lost its blue-green colour. 



These potassium salts show the same association of colour with 

 luminescence as calcspar, quartz, and glass, but all the effects are of 

 a more evanescent character. 



34. A crystal of -potassium chloride was crushed and then flowed 

 into amorphous scales. The scales when placed on the radium cell 

 phosphoresced faintly, and in 30 minutes were tinted with a red- 

 violet. In six hours the colour had deepened. On removal from the 

 rays there was secondary phosphorescence, but both this and the 

 colour disappeared more quickly than had been the case with the more 

 massive crystal. 



35. A small crystal of calcspar was crushed and then flowed into 

 amorphous scales. The scales were placed on the radium cell. They 

 phosphoresced very faintly, and there was no obvious increase over 

 a period of three hours' exposure. Removed from the rays there was 

 faint secondary phosphorescence, and when heated to rather below 

 100 they glowed with a bright orange phosphorescence and continued 

 to do so for some minutes. 



36. In the last two observations, after making due allowance for 

 the small quantities employed and their fine state of division, it 

 appears that the fact of a substance being in the amorphous instead 



