Heroes of the Telegraph

Siemens's researches on this subject, as published in the JOURNAL OF THE SOCIETY OF TELEGRAPH ENGINEERS (Vol. I., p. 123, and Vol. III., p. 297), included a set of curves graphically representing the relation between temperature and electrical resistance in the case of various metals. The electric pyrometer, which is perhaps the most elegant and original of all William Siemens's inventions, is also the link which connects his electrical with his metallurgical researches. His invention ran in two great grooves, 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. Siemens might have been two men, if we are to judge by the work he did; and either half of the twin-career he led would of itself suffice to make an eminent reputation. The success of his metallurgical enterprise no doubt reacted on his telegraphic business. The making and laying of the Malta to Alexandria cable gave rise to researches on the resistance and electrification of insulating materials under pressure, which formed the subject of a paper read before the British Association in 1863. The effect of pressure up to 300 atmospheres was observed, and the fact elicited that the inductive capacity of gutta-percha is not affected by increased pressure, whereas that of india-rubber is diminished. The electrical tests employed during the construction of the Malta and Alexandria cable, and the insulation and protection of submarine cables, also formed the subject of a paper which was read before the Institution of Civil Engineers in 1862.