Masterpieces of Science 



other end of the line I stood upon a wooden 

 board. I requested Mr. Gower to sing a contin- 

 uous musical note, and to my surprise the sound 

 was very distinctly audible from the telephone 

 in my hand. Upon examining my feet I dis- 

 covered that a single blade of grass was bent over 

 the edge of the board, and that my foot touched 

 it. The removal of this blade of grass was fol- 

 lowed by the cessation of the sound from the 

 telephone, and I found that the moment I 

 touched with the toe of my boot a blade of grass 

 or the petal of a daisy the sound was again 

 audible. 



The question will naturally arise, Through 

 what length of wire can the telephone be used ? 

 In reply to this I may say that the maximum 

 amount of resistance through which the undula- 

 tory current will pass, and yet retain sufficient; 

 force to produce an audible sound at the distant 

 end, has yet to be determined; no difficulty, has, 

 however, been experienced in laboratory ex- 

 periments in conversing through a resistance of 

 60,000 ohms, which has been the maximum at my 

 disposal. On one occasion, not having a rheostat 

 [for producing resistance] at hand, I passed 

 the current through the bodies of sixteen persons, 

 who stood hand in hand. The longest length of 

 real telegraph line through which I have at- 

 tempted to converse has been about 250 miles. 

 On this occasion no difficulty was experienced 

 so long as parallel lines were not in operation. 

 Sunday was chosen as the day on which it was 

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