In January 1850, a paper on telegraph lines and apparatus, in which the theory of the electro-static charge in insulated wires, as well as methods and formula: for the localising of faults in underground wires were first established. In 1851, the firm erected the first automatic fire telegraphs in Berlin, and in the same year, Werner Siemens wrote a treatise on the experience gained with the underground lines of the Prussian telegraph system. The difficulty of communicating through long underground lines led him to the invention of automatic translation, which was afterwards improved upon by Steinheil, and, in 1852, he furnished the Warsaw-Petersburg line with automatic fast-speed writers. The messages were punched in a paper band by means of the well-known Siemens' lever punching apparatus, and then automatically transmitted in a clockwork instrument.

In 1854 the discovery (contemporaneous with that of Frischen) of simultaneous transmission of messages in opposite directions, and multiplex transmission of messages by means of electro-magnetic apparatus. The 'duplex' system which is now employed both on land lines and submarine cables had been suggested however, before this by Dr. Zetsche, Gintl, and others.

In 1856 he invented the Siemens' magneto-electric dial instrument giving alternate currents. From this apparatus originated the well- known Siemens' armature, and from the receiver was developed the Siemens' polarised relay, with which the working of submarine and other lines could be effected with alternate currents; and in the same year, during the laying of the Cagliari to Bona cable, he constructed and first applied the dynamometer, which has become of such importance in the operations of cable laying.

In 1857, he investigated the electro-static induction and retardation of currents in insulated wires, a phenomenon which he had observed in 1850, and communicated an account of it to the French Academy of Sciences.

'In these researches he developed mathematically Faraday's theory of molecular induction, and thereby paved the way in great measure for its general acceptance.' His ozone apparatus, his telegraph instrument working with alternate currents, and his instrument for translating on and automatically discharging submarine cables also belong to the year 1857. The latter instruments 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 discovery of importance, and naturally follows from Faraday's far greater and more original discovery of magneto-electric generation.