In 1848, when the war broke out with Denmark, he was sent to Kiel where, together with his brother-in-law, Professor C. Himly, he laid the first submarine mines, fired by electricity and thus protected the town of Kiel from the advance of the enemies' fleet.

Of late years the German Government has laid a great network of underground lines between the various towns and fortresses of the empire; preferring them to overhead lines as being less liable to interruption from mischief, accident, hostile soldiers, or stress of weather. The first of such lines was, however, laid as long ago as 1848, by Werner Siemens, who, in the autumn of that year, deposited a subterranean cable between Berlin and Frankfort-on-the-Main. Next year a second cable was laid from the Capital to Cologne, Aix-la-Chapelle, and Verviers.

In 1847 the, subject of our memoir had, along with Mr. Halske, founded a telegraph factory, and he now left the army to give himself up to scientific work and the development of his business. This factory prospered well, and is still the chief continental works of the kind. The new departure made by Werner Siemens was fortunate for electrical science; and from then till now a number of remarkable inventions have proceeded from his laboratory.