nson also undertook
experiments during the last twenty years, in which they used
induction, but the most remarkable attempts are perhaps those of
Professor Emile Rathenau. With the assistance of Professor Rubens and
of Herr W. Rathenau, this physicist effected, at the request of the
German Ministry of Marine, a series of researches which enabled him,
by means of a compound system of conduction and induction by
alternating currents, to obtain clear and regular communications at a
distance of four kilometres. Among the precursors also should be
mentioned Graham Bell; the inventor of the telephone thought of
employing his admirable apparatus as a receiver of induction phenomena
transmitted from a distance; Edison, Herr Sacher of Vienna, M. Henry
Dufour of Lausanne, and Professor Trowbridge of Boston, also made
interesting attempts in the same direction.

In all these experiments occurs the idea of employing an oscillating
current. Moreover, it was known for a long time--since, in 1842, the
great American physicist Henry proved that the discharges from a
Leyden jar in the attic of his house caused sparks in a metallic
circuit on the ground floor--that a flux which varies rapidly and
periodically is much more efficacious than a simple flux, which latter
can only produce at a distance a phenomenon of slight intensity. This
idea of the oscillating current was closely akin to that which was at
last to lead to an entirely satisfactory solution: that is, to a
solution which is founded on the properties of electric waves.

Sec. 5

Having thus got to the threshold of the definitive edifice, the
historian, who has conducted his readers over the two parallel routes
which have just been marked out, will be brought to ask himself
whether he has been a sufficiently faithful guide and has not omitted
to draw attention to all essential points in the regions passed
through.

Ought we not to place by the side, or perhaps in front, of the authors
who have devised the practical appliances, those scholars who have
constructed the theories and realised the laboratory experiments of
which, after all, the apparatus are only the immediate applications?
If we speak of the propagation of a current in a material medium, can
one forget the names of Fourier and of Ohm, who established by
theoretical considerations the laws which preside over this
propagation? When one looks at the phenomena of induction, would it
not be just to remember that Ar