mewhat burning one,
and no attempt will be made here to deal with the merits or demerits of the
claims made for the respective systems. A series of articles describing the
production of undamped waves and their efficiency in working compared with
damped waves will be found in the _Wireless World_, Nos. 3 and 4, 1913, and
are well worth reading by any one interested in the subject.

[Illustration: FIG. 16.]

A diagrammatic representation of the apparatus as arranged by Professor
Korn is given in Fig. 16. The undamped or "continuous" waves are generated
by means of a high-frequency alternator or Poulsen arc. In Fig. 16, X is
the generator, F inductance, C condenser; the aerial inductance T is
connected by the aerial A and earth E. By this means the waves are tuned to
a certain period. {32} A metal print, similar to what has already been
described, is wrapped round the drum D of the machine, and when the stylus
Z traces over an insulating strip the waves generated are in tune with the
receiving station, but when it traces over a conducting strip, a portion of
the inductance T is short-circuited, the period of the oscillations is
altered, and the two stations are thrown out of tune.

The receiving station is provided with an aperiodic circuit, which consists
of an inductance F', condenser C', and a thermodetector N. A string
galvanometer H (described in Chapter III.), and the self-induction coils B,
B' are connected as shown, the coils B, B' preventing the high-frequency
currents, which change their direction, from flowing through the
galvanometer. The manner in which the string galvanometer is arranged to
reproduce a transmitted picture is shown in Fig. 24.

The connections adopted by the Poulsen Company for photographically
recording wireless messages are given in Fig. 17, a string galvanometer of
the Einthoven type being used. The two self-induction coils S and S' are in
circuit with the detector D and the galvanometer G. The condenser C'
prevents the continuous current produced by the detector from flowing
through the high frequency circuit; P is the primary of the aerial {33}
inductance and F the secondary. The method of transmitting adopted by
Professor Korn appears to be a simple and reliable arrangement, provided
that an equally reliable method of producing the undamped waves can be
found. Owing to the absence of mechanical inertia it should be capable of
working at a good speed, while the absence of a number of p