24 PHOSPHORESCENCE BY HEAT. 
Paper is also capable of becoming lumimous 
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 im the 
dark until the paper is cool. 
