THE CARBON MICROPHONE 



165 



both as a transmitter and as a receiver. It was, however, very 

 Inefficient and Bell himself suggested that some other principle such 

 as that of variation of electrical resistance might overcome the 

 difficulty. He therefore devised the liquid transmitter In which a 

 small platinum wire (Fig. 2), attached to a drumhead of gold-beaters 



Fig. 2 — Bell's liquid transmitter. 



skin, is dipped into a small quantity of acidulated water in a con- 

 ducting cup. The extent of the area of contact between the liquid 

 and the wire is altered by the motion of the latter, thus altering the 

 resistance in a continuous manner. It was with this instrument that 

 the first complete sentence, "Mr. Watson come here — I want you," 

 was successfully transmitted on March 10, 1876. This achievement 



