THE TELEPHONE AND HOW IT WORKS. 



565 



the speaker at the other end could be distinguished so long as silence 

 was maintained in the room, or so long as no heavy lorry rumbling 

 over the stones outside sent in harsh noises which drowned the faint 

 whisper of the instrument. The resistance was gradually raised to 

 4,000 ohms nearly 300 miles with like favorable results ; and for 

 some little distance beyond, articulation could still be made out. But, 

 by the time 10,000 ohms had been applied, putting the speaker at a 

 distance of, say, 700 miles, sound only, but not articulate sound, 

 reached the ear. The tone was there, and every inflection of the 

 voice could be followed ; but articulation was absent, although the 

 listener strained every nerve to catch the sound, which the speaker, as 



Fig. 8. 



was afterward ascertained, was shouting in a loud, clear voice. The 

 prolonged notes of an air sung could be heard with the resistance 

 named, but again no words could be distinguished." 



The next experiment was to join up the telephones in the office 

 with different line-wires in succession going to various distances, and 

 working with different kinds of telegraph-instruments. " When this 

 was done, the real obstacle to telephonic progress at once asserted 

 itself in the shape of ' induction.' The first wire experimented with 

 was partly 'overhouse' and partly underground, and the offices upon 

 it were working A B C, or printing-instruments. It is difficult to ren- 

 der clear to the person ignorant of telegraphic phenomena the idea 



