The _Evening Bulletin_ of the 29th October has the following:
This afternoon a series of experiments were conducted at the Public
Buildings which will be of great interest to electricians all over the
country, and upon which the success of a number of underground
telegraph projects in different parts of the United States depends. In
all projects of this kind the problem which has given most trouble to
inventors has been to overcome the induction. In other words, electric
currents will leave their original conductors and pass to other
conductors which may be near at hand. This interchange of currents may
take place without seriously hindering ordinary telegraphy, as the
indicators are not delicate enough to detect the induction. When
telephones came into use, however, the induction became a great source
of trouble to electricians, it often being the case that the sounds
and influences from without were sufficient to drown out sounds in a
telephone. To-day's experiment was conducted by Mr. J.F. Shorey, a
well-known electrician, who exhibited Dr. Orazio Lugo's cables for
electric light, telephone, and telegraphic purposes.
A large number of prominent electricians were present, including the
following: General J.H. Wilson, President of the N.Y. and N.E.
Railroad, of Boston; Messrs. Frank L Pope, S.L.M Barlow, George B.
Post, Charles G. Francklyn, Col. J.F. Casey, W.H. Bradford, and Selim
R. Grant, of New York; James Gamble, General Manager of the Mutual
Union Telegraph Co.; T.E. Cornich and W.D. Sargent, of the Bell
Telegraph Co.; S.S. Garwood and J.E. Zeublen, of the Western Union,
and others.
The principal tests were made through the conduits on Market Street,
laid by the National Underground Electric Company as far as Ninth
Street. A cable of five conductors was laid through the conduit. Two
of these conductors consisted of simple "circuit wires," while the
other three were what is known as "solenoids." A solenoid wire is a
single straight wire, connected at each end with and wound closely
around by another insulated wire, this forming a complete system, the
electric currents returning into themselves. Electricians claim that
the solenoid effectually overcomes all induction, and this afternoon
experiments were made for the purpose of proving that assertion. In
the telephones, connected by the ordinary wires, a constant burr and
click could be heard, that sound being the induction from the wires on
the poles on Market Street, sixty feet overhead. With the solenoid the
only sound in the telephones was the voices of the persons speaking.
The faintest whispers could be heard distinctly, and the ease and
comfort of conversation was in marked contrast to the other telephone
on the ground wires. A set of telegraph indicators was also attached
to the wires in use in the cable. The sounds were transferred from one
"ground wire" to the other, while the solenoids seemed to resist every
influence but that directed upon them by the operators. Another
interesting test was made. The electric current for a Hauckhousen lamp
was passed through a long coil of solenoid wire. Separated from this
coil by a single newspaper, lay a coil of wire attached to telephones,
yet not a sound could be heard in the telephones but the voices of the
persons using them. The current of electricity created by a
dynamo-electric machine is of necessity a violent one, and in the use
of ordinary wires the induction would be so great that no other sounds
could possibly be heard in the telephones.
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