In the first method, it is not necessary to withdraw the safety key till just before dipping; in the second method the safety key line is belayed at about twenty fathoms, and the key withdrawn when the line is tautened by the ship going ahead. _Tactics._--Description of the various attacks that may be made with the Harvey torpedo against a ship at anchor or under way. In the following diagrams _T_ is the torpedo vessel, _S_ the ship attacked. [Illustration] ...... The track. ------ The tow rope. O-o-o The torpedo. _Attacking a Vessel moored Head and Stern._--In this case the torpedo vessel steers in for the bow or quarter of the vessel attacked, according to the direction of the current, and on the side approached launches the torpedo between the moorings, as at _A_; leaving the tow rope slack, the torpedo vessel proceeds ahead or astern against the current, and when at a sufficient distance off, the tow rope is held fast, which will cause the torpedo to diverge into contact with the vessel attacked, as shown by Fig. 110. _Attacking a Vessel at Anchor by Crossing her Bow._--In this case the torpedo is sufficiently diverged when near to the vessel with a good scope of tow rope out. After having crossed her bow, proceeding onwards, the tow rope will be brought obliquely across her cable, and the torpedo will swing into her, as shown at Fig. 111. It may be here remarked, that in all cases the depth of the explosion can be obtained by the sudden slacking of the tow rope; and the tow rope once under the keel, causes the torpedo to be hauled down near to it before exploding. _Attacking a Vessel at Anchor by coming up from Astern on either Side._--In this case the torpedo is launched when on the quarter of the vessel attacked, as at _A_, the tow rope left slack. After steaming ahead some distance, hold fast the tow rope, when, by continuing to steam on, the torpedo will diverge into contact with the bottom of the vessel attacked, as shown at Fig. 112. _When skilfully performed_, the total destruction of the enemy is certain, since the torpedo is springing from a depth to the surface, and will, in consequence, strike near her keel. The torpedo vessel can pass at her greatest speed, and, if thought necessary, near enough to clear away any of the ordinary obstructions, such as booms, nets, &c. _Passing Down between Two Lines of Vessels at Anchor._--In this case it would be impossible to fire at the torpedo vessel, for fear of injury to their friends. Two or more torpedo vessels following each other with preconcerted signals would cause great destruction. See Fig. 113.