then, turn to the question of Vibrations or Waves in Ether. In
scientific language the length of a wave is the distance from the crest
of one wave to that of the wave immediately following it. Now modern
science recognizes a long series of waves in ether, commencing with the
smallest yet known measuring 0.1 micron, or about 1/254,000 of an inch,
in length, measured by Professor Schumann in 1893, and extending to
waves of many miles in length used in wireless telegraphy--for instance
those employed between Clifden in Galway and Glace Bay in Nova Scotia
are estimated to have a length of nearly four miles. These
infinitesimally small ultra-violet or actinic waves, as they are called,
are the principal agents in photography, and the great waves of wireless
telegraphy are able to carry a force across the Atlantic which can
sensibly affect the apparatus on the other side; therefore we see that
the ether of space affords a medium through which energy can be
transmitted by means of vibrations.

But what starts the vibrations? Hertz announced his discovery of the
electro-magnetic waves, now known by his name, in 1888; but, following
up the labours of various other investigators, Lodge, Marconi and others
finally developed their practical application after Hertz's death which
occurred in 1894. To Hertz, however, belongs the honour of discovering
how to generate these waves by means of sudden, sharply defined,
electrical discharges. The principle may be illustrated by dropping a
stone in smooth water. The sudden impact sets up a series of ripples all
round the centre of disturbance, and the electrical impulse acts
similarly in the ether. Indeed the fact that the waves flow in all
directions from the central impulse is one of the difficulties of
wireless telegraphy, because the message may be picked up in any
direction by a receiver tuned to the same rate of vibration, and the
interest for us consists in the hypothesis that thought-waves act in an