She is armed with a contact torpedo charged with dynamite carried on a 10-foot ram, lying deeply under the water line. To protect the vessel from the effects of the discharge of the torpedo, she is built with two complete parts, sliding one within the other, and having a considerable extent of intermediate space between them. This space is filled with a tough and elastic material (cork and marine glue), which even in the case of the bows being carried away, would afford a second line of resistance. The _Uhlan_ carries an engine of one thousand indicated horse power. The steam is supplied by Belleville's tubular generator. These engines occupy by far the greater space of the vessel, only a very small portion being left for her crew and coal. This great power of the engines is necessitated by the fact that she has to be driven at a very high speed, at the same time she has a very great draught, also the greatest facility of steering has to be attained; hence the proportion of width to length, 25 to 70 feet. In order to save the crew at the worst, a raft is constructed, which is also filled with a mixture of cork and marine glue, and is placed near the helm. The mode of operating with the _Uhlan_ is as follows:-- The dynamite torpedo is affixed to the point of the ram by the aid of divers. The rudder is then fixed, and the crew opening a wide port on the vessel's side, jump on the aforesaid raft. The steamer then rushes forward, and explodes its torpedo in contact with the hostile vessel. The crew hold on to the torpedo ship, and in case she is not injured board her again and repeat the manoeuvre, if necessary.[M] This is a novel form of torpedo boat, but does not seem to be a very practicable method of torpedo attack. _Admiral Porter's Torpedo Ship Alarm._--The _Alarm_ torpedo ship was built from plans designed by Admiral David D. Porter, U.S.N. Her total length, which includes a ram 32 feet long, is 172 feet; her beam is 27 feet 6 inches, and her draught of water is 11 feet. She is built of iron on the bracket plate system, that is to say, she has a double hull, one shell being constructed inside the other. Her double bottom is divided into a number of water-tight compartments. The whole interior of the vessel is also built in compartments, which may be hermetically closed, so that in case of both the shells being ruptured, it would still be impossible to fill the entire ship with water. She is steered by the same apparatus which propels her, viz. the Fowler wheel, which is illustrated at Fig. 145.