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 engine 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
