To prepare the torpedo for use, unscrew the fuze pillar _f_, take off the horizontal bar _k_, place a percussion cup on the nipple _i_, and screw it tightly against the end of the steel rod _g_. The fuze pillar is then ready for use, and should be screwed into the body _a_. Then fill the torpedo with the explosive and close the loading hole _b_. The hammer _n_ is then set by drawing it back and bringing the end of the lever _m_ against it, at the same time running the screw barrel _l_ under the lever _m_, so that its end catches the screw of the barrel, as shown in the figure. The safety pin _o_ is then put in its place and secured by a few parts of thread, which by a sharp jerk on the safety line will be easily broken. [Illustration: DRIFTING TORPEDOES. PLATE XXIX] The horizontal lever _k_, which carries the lever _m_ and propeller _e_, rotates on the top of the fuze pillar _f_, and is prevented from rising by means of a screw. The torpedo being let go, the safety pin _o_ is pulled out by means of a line which is attached to it. The propeller will not revolve whilst the torpedo is drifting with the current, but the instant it is stopped by the action of the current the wheel will be caused to revolve, and after a few revolutions it will unscrew the barrel from under the end of the lever _k_, and the latter, dropping the hammer _n_, will be forced by the spring _p_ into contact with the thin steel plate _h_ on the top of the fuze pillar, which blow is transmitted by means of the steel rod _g_ to the percussion cap, and the torpedo exploded. _American Extempore Drifting Torpedo._--This form of drifting torpedo, which is readily made, was used in great numbers by the Confederates, and though not successful in sinking any Federal ships, caused their vessels considerable annoyance and delay. At Fig. 103 is shown a sketch of this torpedo. It consists of a tin case containing about 70 lbs. of powder. A stiff wire _a_, _b_ passes through a hole punctured in a strip of tin _c_, and a stuffing box _d_; the end _a_ of the wire is covered with fulminate, and so arranged that the friction caused by its passage through the strip of tin _c_ will ignite it; a number of wires lead from _b_ to pieces of driftwood on the surface _e_, _e_, _e_, and the case is supported at the proper depth by a line attached to a section of log. _Towing Torpedoes._--By towing torpedoes are meant those submarine machines which are so shaped and arranged, that when towed from a ship or boat in motion they will diverge to a considerable extent, thus enabling the towing vessel to pass clear of the ship attacked, and yet near enough to allow of the torpedo being brought in contact with some part or other of her hull. Towing torpedoes were for the first time employed on actual service during the late Russo-Turkish war, when a modified form of the well-known Harvey torpedo, designed by a German officer, was used by the Russians, but in no case was it successful.