On speaking into the mouthpiece, the iron
diaphragm vibrates with the voice in the magnetic field of the pole, and
thereby excites the undulatory currents in the coil, which, after
travelling through the wire to the distant place, are received in an
identical apparatus. [This form was patented January 30, 1877.] In
traversing the coil of the latter they reinforce or weaken the magnetism
of the pole, and thus make the disc armature vibrate so as to give out
a mimesis of the original voice. The sounds are small and elfin, a
minim of speech, and only to be heard when the ear is close to the
mouthpiece, but they are remarkably distinct, and, in spite of a
disguising twang, due to the fundamental note of the disc itself, it is
easy to recognise the speaker.
This later form was publicly exhibited on May 4, 1877 at a lecture given
by Professor Bell in the Boston Music Hall. 'Going to the small
telephone box with its slender wire attachments,' says a report, 'Mr.
Bell coolly asked, as though addressing some one in an adjoining room,
"Mr. Watson, are you ready!" Mr. Watson, five miles away in Somerville,
promptly answered in the affirmative, and soon was heard a voice singing
"America."....Going to another instrument, connected by wire with
Providence, forty-three miles distant, Mr.
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