In 1864, during the American civil war, a submarine boat succeeded in sinking the Federal frigate _Housatonic_. This boat, however, was hardly an unqualified success, as, running into the hole made by its torpedo, it went down with the ship; and three crews had previously been lost while carrying out its initial experiments. Since then, many methods of submersion have been tried; but it is only within recent years that naval powers have awakened to the fact that a submersible boat, though by no means so formidable for offensive purposes as its name at first leads one to believe, is a factor which might have to be taken into consideration in the next naval war. Modern types of these boats are the Holland, Nordenfelt, Tuck, and Goubet. The Holland boat comes to us from over the Atlantic, and is peculiar in its weapon of offence. It is fifty feet long, eight feet in diameter, and is driven by a petroleum engine carrying sufficient fuel for two days' run. The diving is effected by means of two horizontal rudders, one on each side of the stern. This only allows of submersion when the boat is in motion; and the boat cannot be horizontal while submerged. It carries ten-inch gelatine blasting shells, fired from a pneumatic gun twenty feet long, whose radius of action is two hundred yards under water and one thousand yards above. The use of gelatine is also objectionable, as the confined space and the vibration of the boat prevent such explosives being carried without some risk of premature explosion. It is for this reason that gun-cotton is adopted in torpedo work, as it will not explode on concussion, and is little affected by change of temperature.