d up_ by a physical contrivance, carried a
thousand miles through a thread of wire not a quarter of an inch in
diameter, and delivered in its integrity to the sense of another
waiting to receive it! At all events, the history of the telephone,
belonging so distinctly to our own age, will stand as a reminder to
after times of the great stride which the human race made in inventive
skill and scientific progress in the last quarter of the nineteenth
century.

The telephone, like many similar instruments, was the work of several
ingenious minds directed at nearly the same time to the same problem.
The solution, however, must be accredited first of all to Elisha P.
Gray, of Chicago, and Alexander Graham Bell, of the Massachusetts
Institute of Technology. It should be mentioned, however, that Amos E.
Dolbear, of Tufts College, Massachusetts, and Thomas A. Edison, of
Menlo Park, New Jersey, likewise succeeded in solving the difficulty
in the way of telephonic communication, and in answering practically
several of the minor questions that hindered at first the complete
success of the invention. The telephone is an instrument for the
reproduction of sounds, particularly the sounds of the human voice, by
the agency of electrical conduction at long distances from the origin
of the vocal disturbance. Or it may be defined as an instrument for
the _transmission_ of the sounds referred to by the agencies
described. Indeed it were hard to say whether in a telephonic message
we receive a _reproduced_ sound or a _transmitted_ sound. On the
whole, it is more proper to speak of a reproduction of the original
sound by transmission of the waves in which that sound is first
written.

It is now well known that the phenomenon called sound consists of a
wave agitation communicated through the particles of some medium to
the organ of hearing. Every particular sound has its own physical
equivalent in the system of waves in which it is written. The only
thing, therefore, that is necessary in order to carry a sound in its
integrity to any distance, is to transmit its physical equivalent, and
to redeliver that equivalent to some organ of hearing capable of
receiving it.

Upon these principles the telephone was produced--created. Every sound
which falls by impact upon the sheet-iron disk of the instrument
communicates thereto a sort of tremor. This tremor causes the disk to
approach and recede from the magnetic pole placed just behind the
diaphra