to the telephone, we again meet a condition
that calls for thoughtful consideration before we can properly
appreciate how much the growth of this industry owes to Edison's
inventive genius. In another place there has already been told the story
of the telephone, from which we have seen that to Alexander Graham
Bell is due the broad idea of transmission of speech by means of an
electrical circuit; also that he invented appropriate instruments and
devices through which he accomplished this result, although not to that
extent which gave promise of any great commercial practicability for
the telephone as it then existed. While the art was in this inefficient
condition, Edison went to work on the subject, and in due time, as we
have already learned, invented and brought out the carbon transmitter,
which is universally acknowledged to have been the needed device that
gave to the telephone the element of commercial practicability, and
has since led to its phenomenally rapid adoption and world-wide use. It
matters not that others were working in the same direction, Edison was
legally adjudicated to have been the first to succeed in point of
time, and his inventions were put into actual use, and may be found in
principle in every one of the 7,000,000 telephones which are estimated
to be employed in the country at the present day. Basing the statements
upon facts shown by the Census reports of 1902 and 1907, and adding
thereto the growth of the industry since that time, we find on a
conservative estimate that at this writing the investment has been not
less than $800,000,000 in now existing telephone systems, while no fewer
than 10,500,000,000 talks went over the lines during the year 1908.
These figures relate only to telephone systems, and do not include any
details regarding the great manufacturing establishments engaged in
the construction of telephone apparatus, of which there is a production
amounting to at least $15,000,000 per annum.

Leaving the telephone, let us now turn our attention to the telegraph,
and endeavor to show as best we can some idea of the measure to which it
has been affected by Edison's inventions. Although, as we have seen in
a previous part of this book, his earliest fame arose from his great
practical work in telegraphic inventions and improvements, there is no
way in which any definite computation can be made of the value of his
contributions in the art except, perhaps, in the case of his quadruplex,