A, @. Bell— Production of Sound by Radiant Energy. 477 
selenium, has its electrical resistance affected by light, and we 
have attempted to utilize this substance in place of selenium. 
The arrangement of cell (shown in fig. 7) was constructed for 
this purpose in the early part of 1880; but we failed at that 
oa 
time to obtain any indications of sensitiveness with a reflecting 
galvanometer. We have since found, however, that when this 
the tellurium cell with the battery in the primary circuit of an 
induction coil, and placing the telephone in the secondary 
rent passed through it, in which case lamp-black could be em- 
ployed in place of selenium in an electrical receiver. This has 
