exhaustive work named _La Telegraphie sans fil_. Among the
reports presented to the Congres international de physique (Paris,
1900), Signor Righi, an illustrious Italian scholar, whose personal
efforts have largely contributed to the invention of the present
system of telegraphy, devoted a chapter, short, but sufficiently
complete, of his masterly report on Hertzian waves, to the history of
wireless telegraphy. The same author, in association with Herr
Bernhard Dessau, has likewise written a more important work, _Die
Telegraphie ohne Draht_; and _La Telegraphie sans fil et les ondes
Electriques_ of MM. J. Boulanger and G. Ferrie may also be consulted
with advantage, as may _La Telegraphie sans fil_ of Signor Dominico
Mazotto. Quite recently Mr A. Story has given us in a little volume
called _The Story of Wireless Telegraphy_, a condensed but very
precise recapitulation of all the attempts which have been made to
establish telegraphic communication without the intermediary of a
conducting wire. Mr Story has examined many documents, has sometimes
brought curious facts to light, and has studied even the most recently
adopted apparatus.

It may be interesting, by utilising the information supplied by these
authors and supplementing them when necessary by others, to trace the
sources of this modern discovery, to follow its developments, and thus
to prove once more how much a matter, most simple in appearance,
demands extensive and complex researches on the part of an author
desirous of writing a definitive work.

Sec. 2

The first, and not the least difficulty, is to clearly define the
subject. The words "wireless telegraphy," which at first seem to
correspond to a simple and perfectly clear idea, may in reality apply
to two series of questions, very different in the mind of a physicist,
between which it is important to distinguish. The transmission of
signals demands three organs which all appear indispensable: the
transmitter, the receiver, and, between the two, an intermediary
establishing the communication. This intermediary is generally the
most costly part of the installation and the most difficult to set up,
while it is here that the sensible losses of energy at the expense of
good output occur. And yet our present ideas cause us to consider this
intermediary as more than ever impossible to suppress; since, if we
are definitely quit of the conception of action at a distance, it
becomes inconceivable to us that e