CHAPTER VII.TAKING UP MINES.
Mines should be raised in the reverse order from that in which they were planted if the conditions of wind and tide are favorable. With a cross tide or a strong cross wind, the mines should be taken up in regular order from one side so that the planter will not drift onto the mine field.
A yawl or launch takes position at the outer mine on each side. The mine-buoy rope is hauled up taut in order to locate the exact position of the mine. The boat holds fast until directed from the planter to let go. While the anchor and mine are being taken aboard the planter, the boat remains off the bow to render assistance if necessary.
The distribution box is raised by underrunning the multiple cable, or by means of its raising rope if the buoy has not been removed. The box is taken aboard the distribution box boat, the lid is removed, and the mine cables, in turn, disconnected from the multiple cable. The planter passes close to the distribution box boat. A heaving line which has been made fast to the outer mine cable is thrown to the bow of the planter. If this should fail, a man throws a heaving line from the bow of the planter. If the conditions be unfavorable for passing a heaving line, a launch may carry the line to the planter. The heaving line attached to the cable is hauled aboard and the cable placed over the cathead. The planter then proceeds to underrun the cable. If the water be shallow, the cable is carried through a snatchblock to the aft deck and coiled, or it may be carried to a cable-reel forward. If the water be deep, or the cable can not be raised easily by hand, it is carried through a snatchblock to the drum of a hoisting windlass and coiled asbefore mentioned. (If placed on a cable-reel, the ends should be insulated and tagged. Mine cables Nos. 1 to 9 should be placed on one reel and Nos. 10 to 19 on another, both reels being carefully marked.) When the raising rope is reached, it is carried with the cable over the cathead. The bight of the rope is hauled in quickly, carried through a snatchblock, and a few turns taken on the drum of a hoisting windlass. The rope is untied from the cable as soon as possible. If there be danger of losing the rope, it should be made fast at once. The anchor is raised until within a few feet of the cathead. It is lifted aboard by means of the boom, or by the differential block on the anchor davit.
At the same time a man is sent over the side of the planter near the mine davit (a rope ladder may be used) to secure the hook of the differential block in the sling attached to the maneuvering ring of the mine when it comes to the surface. To bring the mine to the proper place to accomplish this, a man should be ready to secure the mine-buoy rope with a boathook; other men should be ready to pull the mine forward, if necessary, by means of the cable. The mine is raised by the differential block of the mine davit. It may be raised by the boom and fall; or by means of a tackle secured to the mine davit, the end of the rope running through a snatchblock to the drum of a windlass. The distance weight of the automatic anchor may be raised by the fall of the boom, or by an improvised tackle. An eye should be made in the distance rope for this purpose.
If the end of the cable is lost, the work may proceed as follows: The planter moves out to the mine if its buoy is still in place. A sling made of raising rope may be thrown over the mine, or two raising ropes are tied together and one end is passed to a launch which moves around the mine and brings the end back to the planter. Both ends are placed over the cathead, through a snatchblock, and around the drum of a hoisting windlass. The mine is hoisted, bail up, until near the cathead. It can then be transferred to the anchor davit. The mine cable is pulled in until the raising rope is reached. The work then proceedsas before. If the mine buoy has been removed, a yawl may drag for the cable with a grappling iron. If the raising rope should break or be lost, the mine may be raised as mentioned above, except that the mine must be transferred to the fall of the boom and the anchor raised by means of its mooring rope, or the mine may be transferred to the anchor davit, as before, and a raising rope made fast to the mooring rope of the anchor and carried over the cathead, through a snatchblock, to a hoisting windlass. The mine, as soon as the strain is taken up by the raising rope, is unshackled. The anchor is then taken aboard in the usual manner.
As soon as the mines are taken aboard they are disconnected, the ropes are coiled, and all matériel placed so as not to interfere with subsequent work. As soon as the matériel is unloaded on the wharf it should be cleaned thoroughly and stored.
If the multiple cable is to be left down, the ends of the conductors are insulated, the lid replaced, and the box lowered by means of a raising rope, the end of which is made fast to the bight of the bowline of the anchor rope.
If the multiple cable is to be taken up, the end is passed to the planter, run through a large snatchblock on the bow, and coiled on a cable-reel as it is raised. Whenever a multiple cable is coiled on a reel it should be secured so that both ends will be available for test when the cable is stored.
Unloading mines.—Should any of the mines be loaded with dynamite the utmost care must be exercised in unloading them. (See p. 76.) Some contrivance must be rigged up so that the first few turns of the compound plug may be accomplished by the operator at a distance, as there is great liability of explosion, due to leakage of nitroglycerin into the screw threads. After the compound plug is removed the precautions to be observed are given inAppendix No. 1.
Should the mine be loaded with guncotton or trotol, no danger is to be apprehended in unloading; the usual precautions in handling high explosives must, of course, be observed.