598 PROCEEDINGS OF THE AMERICAN ACADEMY. 



has over the test tube being the better control of the temperature, and 

 this is in part offset by the difficulty of keeping the brightest luminescence 

 directly in front of the slit. The heated crystals decrepitate, and break 

 up into smaller fragments, and occasionally a heavier explosion than usual 

 blows everything out of the furnace, or at least disturbs the position of 

 the main mass of luminescent material. The test tube, held in the hand, 

 can be turned so that the brightest part is always toward the slit, and in 

 general the cruder method is at least as easy in the end. 



Spectroscopic Results. 



TABLE I. 



Chlorophane from Amelia Court-House, Va. 



Continuous spectrum from violet to red, with maximum in the green- 

 yellow both visually and in the photographs. Superimposed over this 

 continuous band the following lines and narrow bands : 



5 sharp, 

 diffuse. 



sharp. 



Clear, colorless fluorite from Westmoreland, N. H. Underlying dif- 

 fuse band from green to violet, rather sharply bounded at green end, but 

 shading off in violet. Superimposed over this, and in the yellow and red. 

 the following lines and bands : 



