2.--The plan of releasing the charge at will is effected by means of the small gun _n_, which is fired by electricity, and by its firing forces back the plate _e_, thus releasing the charge, which is then exploded, as previously explained. _Locomotive Torpedoes._--By "Locomotive" torpedoes are meant those that possess within themselves the power to move through the water, when once started in a given direction. Of this species of submarine weapons, the following are the most efficient and are the ones most generally used:-- 1.--The Whitehead fish torpedo. 2.--The Lay torpedo. _Invention and Adoption of the Fish Torpedo._--The idea developed by the fish torpedo is due to an Austrian marine artillery officer, who is now dead. In 1864, Mr. Robert Whitehead, then superintendent of iron works at Fiume, acting upon the suggestions of a Captain Lupuis of the Austrian army, commenced a series of experiments to ascertain the practical value of the above idea, the result being a fish torpedo, commonly called "The Whitehead," which though far inferior to the fish torpedo of the present day, was then considered to be a fearful and wonderful weapon. The Austrians were the first to purchase this weapon, and two years later, in 1870, Mr. Whitehead came to England, and prosecuted numerous experiments with his fish torpedo under the supervision of several English officers, and on the 8th of October of the same year he succeeded in completely destroying an old hulk moored at the mouth of the Medway. The fairly successful results of these experiments induced the English government to purchase the secret and several of Mr. Whitehead's fish torpedoes, under the following conditions:-- 1.--The right of manufacturing them in England. 2.--To be kept fully informed of all improvements, as soon as made. 3.--The right of using all such improvements. And the total amount paid to Mr. K. Whitehead at that time was the sum of seventeen thousand five hundred pounds, which did not include the sum of two thousand five hundred pounds claimed for the expenses attendant on the Medway experiments. Since then a large number of Whitehead's fish torpedoes have been purchased from time to time, especially during the Turco-Russian war, when some two hundred were ordered, also great numbers have been manufactured at Woolwich. The English fish torpedo, as far as can be ascertained, is a vastly superior weapon to the Whitehead fish torpedo, possessing as it does increased speed, and therefore far greater accuracy. Besides Austria and England, nearly all the European governments have purchased the Whitehead secret and torpedoes, but in the case of some of them, the last two clauses of the English conditions of purchase were omitted. [Illustration: WHITEHEAD'S FISH TORPEDO. PLATE XXXVI] The Turkish is the only government that has obtained the Whitehead secret and torpedoes without paying for it. This was managed as follows:--