MORSE. — STUDIES ON PLDORITE. 613 



The results of this investigation may be considered wholly negative, 

 in so far as the explanation of the facts of luminescence in the mineral 

 fluorite is concerned. It has, however, seemed a very necessary step in 

 the series of investigations which is now being carried on with the gen- 

 erous aid of the Rumford Fund. It permits attention to be turned 

 toward other questions with a sense of at least having looked in this 

 direction for the mysterious source of the luminescence phenomena in 

 this substance, fluorite. 



Jefferson Physical Laboratory, 



Harvard University, 



Dec. 27, 1905. 



