Several modes of mooring buoyant submarine mines have been suggested, the most practicable of which are as follows:--
1.--Ladder moorings. 2.--Fore and aft moorings. 3.--Austrian method of mooring. 4.--Single rope mooring.
_Ladder Mooring._--This is a method of mooring, which in places where it may be necessary to place the anchors far apart will be found useful.
The circuit closer is connected to the mine by two ropes which lead thence to two anchors, the ropes being separated by wooden rounds, or spreaders, 1 to 3 feet long, by which the tendency to twisting is prevented.
The anchors are placed some 12 feet apart.
The only defect of the ladder mooring is the quantity of sea-weed, &c., that is liable to be lodged on the rounds, thus causing the circuit closer to be drawn out of its proper position.
_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.