The full divergence of 45° is obtained up to 50 fathoms; beyond that the bight of the tow rope in the water drags the torpedo astern, unless the tow rope is triced much higher up, which has its disadvantage; 40 to 50 fathoms of tow rope gives the best command of the torpedo, veering 2 or 3 fathoms of tow line suddenly will always sink the torpedo some feet below the surface. Should it become necessary to use the torpedoes with a stern board, they can be so used, but in this case the port torpedo is used on the starboard, bow and starboard on the port; all other arrangements being exactly the same. In rough weather, advantage should be taken of the roll, and the torpedo allowed to swing out from the yard, and be let go by the run, checking the tow rope immediately the torpedo is in the water. It is not absolutely necessary to ease the vessel when launching; the torpedo can be launched at full speed. In the event of its being found necessary to cut adrift the torpedo, in consequence of coming suddenly across a friendly vessel, the tow rope should be cut near the brake, and if the buoy rope has been rove through the large stern ring, the torpedo will sink and be lost, the buoy only remaining. If the buoy rope has been rove through the small stern ring, the torpedo will be suspended by the buoy rope; and should the safety key not have been withdrawn, can be recovered with safety. In the event of wishing to recover it when the buoy rope has been rove through the large ring, a toggle must be lashed on the tow rope abaft the leading block on the yard, when it can be recovered by the buoy rope; as a general rule, however, it will be found best to expend the torpedo, and not attempt its recovery. [Illustration: HARVEY'S TOWING TORPEDO. PLATE XXXI] [Illustration: SYSTEMS OF ATTACK WITH HARVEY'S TOWING TORPEDO. PLATE XXXII] _Recovering the Torpedo._--Should the safety key have been withdrawn, great caution is necessary. Tongs, shown at Fig. 109, for going round the upper part of the bolt, to take the place of the safety key, when once clasped and secured round the bolt, render the torpedo safe to handle; this could only be done from a boat. With the safety key in, there is no danger in hoisting it inboard again by its own tow rope, and hoisting up the buoys at the same time with a grapnel. _Different Methods of Using the Torpedo._--There are two methods of employing the torpedo, either of which may be adopted, according to circumstances. 1.--When it is towed with a length of line varying from 25 to 60 fathoms, and dipped when in position to strike the attacked vessel. 2.--When it is kept suspended from the yard, &c., and dropped at the spot, where according to the first method it would have been dipped.