Charles William Siemens (April 4, 1823 - November 19, 1883) was a German-born engineer who for most of his life worked in Britain and later became a British subject. The regenerative furnace is his greatest single invention using the Siemens-Martin process. The electric pyrometer, which is perhaps the most elegant and original of all his inventions, is also the link which connects his electrical with his metallurgical researches. Siemens pursued two major themes in his inventive efforts, one based upon the science of heat, the other based upon the science of electricity; and the electric thermometer was, as it were, a delicate cross-coupling which connected both. He died in 1883 at the age of 60.