Fore and aft Mooring.—This mode may be advantageously employed in a tideway where the current runs very strong, that is to say, five knots per hour, or more. It consists simply of two anchors, one of which is moored up, and the other down the stream.
Austrian Method of Mooring.—This method of mooring, adopted by the Austrians during the war of 1866, is shown at [Fig. 47]. It consists of a wooden triangular platform on which several heavy weights a, a, a are placed; the mine is attached to this platform by means of three wire ropes b, b, b, connected to the angles of the latter, and fastened to three chains, which by means of a catch holds the mine at the position required.
This catch consists of a pulley attached to the extremity of the wire rope of the platform, through which the mooring chain of the mine is passed, and fastened by a key at the required depth by means of a self-acting arrangement.
This key, which is of considerable weight, slips down as the mine is being hauled into position, but the moment the chain is slacked, two arms catch into a link of the chain, and so hold the mine in position. The weight of such a key is about 60 lbs. It is fitted with nuts, &c., to enable it to be taken to pieces.
This plan of mooring proved very effective in the harbours of the Adriatic, where there is hardly any tide or current to twist the mooring ropes, or otherwise disturb the mines. The Austrians have lately adopted the mushroom sinker in place of the wooden platform and weights, for their anchor.
Single Rope Mooring.—This simple method of mooring has after numerous exhaustive experiments been adopted as the most practicable and effective of all others. Whenever possible, a wire instead of hempen cable should be used to connect the mine and its circuit closer to the mooring anchor, as the former is less liable to twist, kink, or wear from friction than the latter.
A ground mine with circuit closer attached is represented at [Fig. 48], where a is the wire mooring rope, b the electric cable leading from the mine to the circuit closer, C, and c the cable leading from the firing station to the mine; d is the oblong sinker attached to the mine, and e the tripping chain leading to the shore, to which the cable c is attached at intervals, so that by underrunning the electric cable, the tripping chain may be easily picked up, and the mine raised.
MOORINGS FOR SUBMARINE MINES.
