ccupied with some minor improvements at Hoyle's Calico Printing Works.
He also engaged in railway works from time to time; and in 1846 he
brought out a double cylinder air-pump, in which the two cylinders are
so combined, that the compressing side of the first and larger cylinder
communicated with the suction side of the second and smaller cylinder,
and the limit of exhaustion was thereby much extended. The invention was
well received at the time, but is now almost forgotten.

Siemens had been trained as a mechanical engineer, and, although he
became an eminent electrician in later life, his most important work at
this early stage was non-electrical; indeed, the greatest achievement of
his life was non-electrical, for we must regard the regenerative furnace
as his MAGNUM OPUS. Though in 1847 he published a paper in Liebig's
ANNALEN DER CHEMIE on the 'Mercaptan of Selenium,' his mind was busy
with the new ideas upon the nature of heat which were promulgated by
Carnot, Clayperon, Joule, Clausius, Mayer, Thomson, and Rankine. He
discarded the older notions of heat as a substance, and accepted it as
a form of energy. Working on this new line of thought, which gave him an
advantage over other inventors of his time, he made his first attempt
to economise heat, by constructing, in 1847, at the factory of Mr.
John Hick, of Bolton, an engine of four horse-power, having a condenser
provided with regenerators, and utilising superheated steam. Two
years later he continued his experiments at the works of Messrs. Fox,
Henderson, and Co., of Smethwick, near Birmingham, who had taken the
matter in hand. The use of superheated steam was, however, attended
with many practical difficulties, and the invention was not entirely
successful, but it embraced the elements of success; and the Society of
Arts, in 1850, acknowledged the value of the principle, by awarding Mr.
Siemens a gold medal for his regenerative condenser. Various papers read
before the Institution of Mechanical Engineers, the Institution of Civil
Engineers, or appearing in DINGLER'S JOURNAL and the JOURNAL OF THE
FRANKLIN INSTITUTE about this time, illustrate the workings of his mind
upon the subject. That read in 1853, before the Institution of Civil
Engineers, 'On the Conversion of Heat into Mechanical Effect,' was
the first of a long series of communications to that learned body, and
gained for its author the Telford premium and medal. In it he contended
that a perfect engi