3.—In the case of buoyant mines, their distance from the bottom must be so adjusted, that at no time shall a vessel passing over them be out of their vertical range of destruction, nor shall they be visible.
The difficulties attendant upon the efficient mooring of submarine mines are immense, as will be understood when the action of gales of wind, and strong tides, which latter vary continually in their direction and in their rise and fall, are taken into consideration.
The foregoing remarks apply more particularly to a system of buoyant submarine mines, as those placed on the ground are comparatively easy to moor.
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.