Briefly reviewing the history of the torpedo during its first period of existence, viz., from Captain Bushnell's invention of submarine magazines in 1775, down to the introduction of electricity, as a means of exploding submarine mines, by Colonel Colt, in 1829, we find that due to the unwearied exertions, and numerous experiments carried out by Captain Bushnell, Mr. R. Fulton and others, the following very important principles in the art of torpedo warfare were fully proved:-- 1.--That a charge of gunpowder could be exploded under water. 2.--That any vessel could be sunk by a torpedo, provided only the charge were large enough. 3.--That it was possible to construct a boat which could be navigated, and remain for several hours under water, without detriment to her crew. 4.--That a ship at anchor could be destroyed, by means of drifting torpedoes, or by a submarine or ordinary boat, armed with a spar torpedo. 5.--That a vessel underweigh could be destroyed by means of stationary submarine mines, and by the harpoon torpedo. These principles, which at the time were fully admitted, laid the foundations of the systems of torpedo warfare, that are at the present day in vogue, all over the world. _Second Epoch._--The second epoch in the life of the torpedo dates from 1829, when Colonel Colt, then a mere lad, commenced experiments with his submarine battery. _Colt's Experiments._--His first public essay, was on the 4th June, 1842, when he exploded a case of powder in New York harbour, while himself standing at a great distance off. Having by numerous successful experiments satisfactorily proved that vessels at anchor could be sunk by means of his electrical mines, Colonel Colt engaged to destroy a vessel underweigh by similar means, which feat he successfully accomplished on 13th April, 1844. _Colt's Electric Cable._--The electric cable as used by Colonel Colt, was insulated by cotton yarn, soaked in a solution of asphaltum and beeswax, and the whole enclosed in a metal case. _Colt's Reflector._--On examining Colt's papers after his death, one was found illustrating one of his many devices for effecting the explosion of a submarine mine at the proper instant.