the barrel at the transmitting station. In this way a facsimile of
the gelatine picture is produced at the distant station, and an
electrotype or cliche of it can be made for printing purposes. The
method is, in fact, a species of electric line graving, and Mr.
Amstutz hopes to apply it to engraving on gold, silver, or any
soft metal, not necessarily at a distance.

We know that an electric current in one wire can induce a
transient current in a neighbouring wire, and the fact has been
utilised in the United States by Phelps and others to send
messages from moving trains. The signal currents are intermittent,
and when they are passed through a conductor on the train they
excite corresponding currents in a wire run along the track, which
can be interpreted by the hum they make in a telephone.
Experiments recently made by Mr. W. H. Preece for the Post Office
show that with currents of sufficient strength and proper
apparatus messages can be sent through the air for five miles or
more by this method of induction.

We come now to the submarine telegraph, which differs in many
respects from the overland telegraph. Obviously, since water and
moist earth is a conductor, a wire to convey an electric current
must be insulated if it is intended to lie at the bottom of the
sea or buried underground. The best materials for the purpose yet
discovered are gutta-percha and india-rubber, which are both
flexible and very good insulators.

The first submarine cable was laid across the Channel from Dover
to Calais in 1851, and consisted of a copper strand, coated with
gutta-percha, and protected from injury by an outer sheath of hemp