The torpedo is blown out of the tube either by compressed air suddenly injected into the rear end, or by an impulse charge of a few ounces of powder, usually cordite. The air pressure varies from 300 to 600 lbs. to the square inch, and the powder charge from 4 oz. to 6½ oz. Submerged tubes are of course tubes below the water-line, and all the most recent ships are fitted with these, as their advantages over above-water tubes are universally recognised. After the Chino-Japanese war all governments, when demanding designs for new warships, made it almost a _sine qua non_ that the torpedoes should be discharged from below water. In firing torpedoes from above-water tubes the torpedo is liable to be hit by the enemy, and it is generally considered that if the tube be hit by even a small projectile it must inevitably explode; the submerged tube affords protection both to the men and the weapon, while the torpedo is less deflected on entering the water. The weight of the submerged tube is some 7 tons, 2 tons more than an above-water one. In order to avoid any possibility of the Whitehead inflicting injury on the vessel firing it, and in order that it may be as little deflected as possible, a guiding bar is run out of the tube by means of pneumatic power when the torpedo has been placed in it. The guiding bar holds and guides the torpedo until quite clear of the ship, when by means of a secret apparatus it releases the torpedo at the end simultaneously; without this arrangement the torpedo would be enormously deflected towards the stern directly it began to leave the tube, and would probably strike the ship from which it had just been fired. Revolving tubes are carried either singly or in pairs on board torpedo-boats and destroyers, and the torpedoes are fired from them by powder impulse only. “Dropping gear” is only used on second-class torpedo boats and picket boats. It consists of a pair of clip tongs suspended from pivoted davits; the tongs being opened, the torpedo falls into the water, the engines are set in motion, and it speeds off to do its deadly work. The torpedoes for the English Admiralty are made at the Royal Gun Factory, by Messrs. Greenwood and Batley, of Leeds, and by Mr. Whitehead’s factory at Portland. Mr. Whitehead has another factory at Fiume, whence he supplies almost all the Great Powers with his torpedoes. In time of war the torpedo would be discharged by an officer in the conning tower; by the aid of a torpedo directory he would make the necessary adjustments and would fire the torpedo down below by pressing his hand on an electric key, thus completing a circuit connected with the firing apparatus in the tube. [Illustration: A BRITISH DESTROYER. ] CHAPTER XV THE NORDENFELT SUBMARINES