74 PROFESSOR BARRETT, 
different qualities of different voices are heard, so that at 50 or 
100 miles distance the individuality of the speaker is transmitted 
as well as his ideas. 
A section of the present form of this important instrument is 
shown in figure 1. A diagrammatic representation of the essential 
parts is given in figure 2: a permanent bar magnet (N.S.) (about 
four inches long), has a coil of fine wire (b) wound at one extremity, 
in front of the coil a disc (a) of thin sheet iron is fixed. The 
transmitting and receiving instruments are precisely alike, and no 
further source of electricity is required than that produced by 
BiG. Le 
Section, 





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SLS7 CG 

