1900, was marking time, awaiting the arrival of a thin wire that
would do the work of a thick one. The importance of the problem
is shown by the fact that one-fourth of all the capital invested
in the telephone has been spent in copper. Professor Pupin, who
had been a member of the faculty of Columbia University since
1888, solved this problem in his quiet laboratory and, by doing
so, won the greatest prize in modern telephone art. His
researches resulted in the famous "Pupin coil" by the expedient
now known as "loading." When the scientists attempt to explain
this invention, they have to use all kinds of mathematical
formulas and curves and, in fact, they usually get to quarreling
among themselves over the points involved. What Professor Pupin
has apparently done is to free the wire from those miscellaneous
disturbances known as "induction." This Pupin invention involved
another improvement unsuspected by the inventor, which shows us
the telephone in all its mystery and beauty and even its
sublimity. Soon after the Pupin coil was introduced, it was
discovered that, by crossing the wires of two circuits at regular
intervals, another unexplainable circuit was induced. Because
this third circuit travels apparently without wires, in some
manner which the scientists have not yet discovered, it is
appropriately known as the phantom circuit. The practical result
is that it is now possible to send three telephone messages and
eight telegraph messages over two pairs of wires--all at the same
time. Professor Pupin's invention has resulted in economies that
amount to millions of dollars, and has made possible long
distance lines to practically every part of the United States.

Thus many great inventive minds have produced the physical
telephone. We can point to several men--Bell, Blake, Carty,