The platinum wire bridge _g_ is 4/10 inch long, while that of the fuze is 3/10 inch, the object of this difference in length of the bridges being to ensure the former one _g_ being fired, and thus the insulation made doubly sure. Many other forms of disconnectors have been devised, but none have proved in practice so effective as the one just described. [Illustration: JUNCTION BOXES. MECHANICAL TURK'S HEAD. PLATE X] _Mooring Electrical Submarine Mines._--This is one of the most difficult problems to be solved in connection with a system of submarine mines. The objects to be attained in mooring are as follows:-- 1.--The mines should preserve the exact positions in which they are laid down. NOTE.--From the comparatively small radius of destructive effect, of even heavily charged submarine mines, it will be understood how absolutely essential, in the case of mines fired by judgment, it is that this object should be attained. 2.--The mooring chains, or ropes, must be so arranged that no twisting whatever should occur, as otherwise fracture of the insulated wire would be likely to happen. 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. _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.