were applied to the Sardinia, Malta, and
Corfu cable.

In 1859, he constructed an electric log; he discovered that a dielectric
is heated by induction; he introduced the well known Siemens' mercury
unit, and many improvements in the manufacture of resistance coils. He
also investigated the law of change of resistance in wires by heating;
and published several formulae and methods for testing resistances
and determining 'faults' by measuring resistances. These methods were
adopted by the electricians of the Government service in Prussia, and by
Messrs. Siemens Brothers in London, during the manufacture of the
Malta to Alexandria cable, which, was, we believe, the first long cable
subjected to a system of continuous tests.

'In 1861, he showed that the electrical resistance of molten alloys is
equal to the sum of the resistances of the separate metals, and that
latent heat increases the specific resistance of metals in a greater
degree than free heat.' In 1864 he made researches on the heating of the
sides of a Leyden jar by the electrical discharge. In 1866 he published
the general theory of dynamo-electric machines, and the principle of
accumulating the magnetic effect, a principle which, however, had been
contemporaneously discovered by Mr. S. A. Varley, and described in
a patent some years before by Mr. Soren Hjorth, a Danish inventor.
Hjorth's patent is to be found in the British Patent Office Library, and
until lately it was thought that he was the first and true inventor of
the 'dynamo' proper, but we understand there is a prior inventor still,
though we have not seen the evidence in support of the statement.

The reversibility of the dynamo was enunciated by Werner Siemens in
1867; but it was not experimentally demonstrated on any practical scale
until 1870, when M. Hippolite Fontaine succeeded in pumping water at the
Vienna international exhibition by the aid of two dynamos connected in
circuit; one, the generator, deriving motion from a hydraulic engine,
and in turn setting in motion the receiving dynamo which worked the
pump. Professor Clerk Maxwell thought this discovery the greatest of the
century; and the remark has been repeated more than once. But it is a
remark which derives its chief importance from the man who made it, and
its credentials from the paradoxical surprise it causes. The discovery
in question is certainly fraught with very great consequences to the
mechanical world; but in itself it is no