ne would be one in which all the heat applied to the
steam was used up in its expansion behind a working piston, leaving none
to be sent into a condenser or the atmosphere, and that the best results
in any actual engine would be attained by carrying expansion to the
furthest possible limit, or, in practice, by the application of a
regenerator. Anxious to realise his theories further, he constructed a
twenty horse-power engine on the regenerative plan, and exhibited it
at the Paris Universal Exhibition of 1855; but, not realising his
expectations, he substituted for it another of seven-horse power,
made by M. Farcot, of Paris, which was found to work with considerable
economy. The use of superheated steam, however, still proved a drawback,
and the Siemens engine has not been extensively used.

On the other hand, the Siemens water-meter, which he introduced in 1851,
has been very widely used, not only in this country, but abroad. It acts
equally well under all variations of pressure, and with a constant or an
intermittent supply.

Meanwhile his brother Werner had been turning his attention to
telegraphy, and the correspondence which never ceased between the
brothers kept William acquainted with his doings. In 1844, Werner,
then an officer in the Prussian army, was appointed to a berth in the
artillery workshops of Berlin, where he began to take an interest in
the new art of telegraphy. In 1845 Werner patented his dial and printing
telegraph instruments, which came into use all over Germany, and
introduced an automatic alarm on the same principle. These inventions
led to his being made, in 1846, a member of a commission in Berlin
for the introduction of electric telegraphs instead of semaphores.
He advocated the use of gutta-percha, then a new material, for the
insulation of underground wires, and in 1847 designed a screw-press for
coating the wires with the gum rendered plastic by heat. The following
year he laid the first great underground telegraph line from Berlin to
Frankfort-on-the-Main, and soon afterwards left the army to engage
with Mr. Halske in the management of a telegraph factory which they had
conjointly established in 1847. In 1852 William took an office in John
Street, Adelphi, with a view to practise as a civil engineer. Eleven
years later, Mr. Halske and William Siemens founded in London the house
of Siemens, Halske & Co., which began with a small factory at Millbank,
and developed in course of time into