Prof. A. Graham Bell of Boston independently discovered the same means
for producing multiple effects over the same wire; but it appears he did
not practically work it out as completely as did Mr. Gray. But while the
latter was chiefly employed in perfecting the method as a telegraphic
system, Prof. Bell had set before himself the more difficult problem of
transmitting speech. This he has actually accomplished, as we have so
often been reminded during the past year.
Thoroughly conversant with the acoustic researches of Helmholtz, and
keeping in mind the complex form of the air vibrations produced by the
human voice, he attempted to make these vibrations produce corresponding
pulsations in an electric current in the manner analogous to the
electric interrupter.
Observing that membranes when properly stretched can vibrate to any kind
of a sound, he sought to utilize them for this purpose. So did Reiss;
but Reiss inserted the vibrating membrane into the circuit, and it was
quite evident that such a plan would not answer, therefore the current
must not be broken; but could an electric current be interfered with
without breaking the connections?
The well-known re-actions of magnets upon electrical currents, first
noted by Oersted, and fully developed by Faraday, gave the clew to the
solution. A piece of iron should be made to vibrate by means of sound
vibrations, so as to affect an electro-magnet and induce corresponding
electrical pulsations.