ints not greatly remote from each other,
and not connected together with wires.

The latter system (described in Chapter XXIII and in a succeeding
article of this Appendix) was based upon the phenomena of
electromagnetic or electrostatic induction between conductors separated
by more or less space, whereby electric impulses of relatively low
potential and low frequency set up in. one conductor were transmitted
inductively across the air to another conductor, and there received
through the medium of appropriate instruments connected therewith.

As distinguished from this system, however, modern wireless
telegraphy--so called--has its basis in the utilization of electric
or ether waves in free space, such waves being set up by electric
oscillations, or surgings, of comparatively high potential and high
frequency, produced by the operation of suitable electrical apparatus.
Broadly speaking, these oscillations arise from disruptive discharges of
an induction coil, or other form of oscillator, across an air-gap, and
their character is controlled by the manipulation of a special type of
circuit-breaking key, by means of which long and short discharges are
produced. The electric or etheric waves thereby set up are detected
and received by another special form of apparatus more or less distant,
without any intervening wires or conductors.

In November, 1875, Edison, while experimenting in his Newark laboratory,
discovered a new manifestation of electricity through mysterious sparks
which could be produced under conditions unknown up to that time.
Recognizing at once the absolutely unique character of the phenomena, he
continued his investigations enthusiastically over two mouths, finally
arriving at a correct conclusion as to the oscillatory nature of the
hitherto unknown manifestations. Strange to say, however, the true
import and practical applicability of these phenomena did not occur to
his mind. Indeed, it was not until more than TWELVE YEARS AFTERWARD, in
1887, upon the publication of the notable work of Prof. H. Hertz proving
the existence of electric waves in free space, that Edison realized the
fact that the fundamental principle of aerial telegraphy had been within
his grasp in the winter of 1875; for although the work of Hertz was more
profound and mathematical than that of Edison, the principle involved
and the phenomena observed were practically identical--in fact, it may
be remarked that some of the methods and