24 PHOSPHORESCENCE BY HEAT. 



Paper is also capable of becoming luminous 

 when heated : fix upon a plate of copper any 

 characters of the same metal ; these characters 

 should be about two-tenths of an inch thick. At 

 the back of the plate fix an iron rod terminating 

 in a wooden handle. When the plate is heated, and 

 then violently pressed upon very dry paper lying 

 upon three or four folds of cloth, the characters 

 thus impressed will appear faintly luminous in the 

 dark until the paper is cool. 



