of soft iron is temporarily magnetised by the passage of an electric
current through a coil surrounding it. This principle was further
applied by Morse in his electro-magnetic printing telegraph. Davy was a
prolific inventor, and also sketched out a telegraph in which the gases
evolved from water which was decomposed by the current actuated a
recording pen. But his most valuable discovery was the 'relay,' that is
to say, an auxiliary device by which a current too feeble to indicate
the signals could call into play a local battery strong enough to make
them. Davy was in a fair way of becoming one of the fathers of the
working telegraph, when his private affairs obliged him to emigrate to
Australia, and leave the course open to Cooke and Wheatstone.



CHAPTER II.

CHARLES WHEATSTONE.

The electric telegraph, like the steam-engine and the railway, was a
gradual development due to the experiments and devices of a long train
of thinkers. In such a case he who crowns the work, making it
serviceable to his fellow-men, not only wins the pecuniary prize, but is
likely to be hailed and celebrated as the chief, if not the sole
inventor, although in a scientific sense the improvement he has made is
perhaps less than that of some ingenious and forgotten forerunner. He
who advances the work from the phase of a promising idea, to that of a
common boon, is entitled to our gratitude. But in honouring the
keystone of the arch, as it were, let us acknowledge the substructure on
which it rests, and keep in mind the entire bridge. Justice at least is
due to those who have laboured without reward.