Page:The Development of Navies During the Last Half-Century.djvu/331

 the extra propeller will give additional power, though in a small vessel this is not found to be the case. For the slower speeds, the centre screw alone working should prove sufficient, while those on each side would be disconnected and freely revolve with the progress of the vessel. Time can alone show whether this assumption is correct.

As regards torpedo boats, up to a very recent date none existed in America; but one has now been completed, 138 ft, long, which attained a speed of 23 knots, and others no doubt will follow. It is curious that up to the present no American war vessel has carried a locomotive torpedo. The Whitehead was not adopted when taken up by other nations, and efforts have for some time been directed to obtain a torpedo of native origin. Several have been put forward, but the most promising is one invented by Captain Howell of the American navy. It is similar in shape to the Whitehead, but instead of being driven by compressed air the Howell torpedo is propelled by two screws actuated by the rapid rotation of a heavy steel flywheel. This is fixed inside the torpedo, and spun to a great velocity, before the torpedo is launched, by an independent motor on board the ship, worked by steam or electricity. The axes of the wheel are connected to the screw shafts, by which power is transmitted to the propellers. This flywheel also acts as a