_Land Service Cable._--The cable employed for this service consists of a core formed similar to that of the multiple cable, described at page 41; over which is laid a padding of hemp, and finally two servings of tarred hemp laid spirally in opposite directions are wound on. Its weight in air is 16 cwt., and in water 4-50/112 cwt. per nautical mile. Its breaking strain 17-1/2 cwt., and cost per nautical mile about £137. _Sea Service Cable._--This consists of a similar core to the land service cable, and padding of hemp, over which is laid an armouring of fifteen No. 13 galvanised iron wires, each one being covered with tarred tape, and finally the ordinary servings of tarred hemp. Its weight in air is 49-101/112 cwt., and in water 25-109/112 cwt. per nautical mile. Its breaking strain 65-100/112 cwt., and cost per nautical mile about £202. When frictional electricity is used to fire high tension fuzes, it has been found by experiment that if several lines of insulated cables are laid in the same trench for a few hundred yards, the inductive effect of the electrical charge generated by a frictional machine is so great that its discharge through one cable is sufficient not only to fire the fuze in immediate connection with it, but by induction every other fuze in connection with the remaining wires laid in the trench. And this effect equally occurs when the electric cables are some feet apart, provided they run parallel for a few hundred yards, and whether the shore ends of the cables, the fuzes in connection with which are not intended to be fired, are insulated, or put directly to earth, the connections beyond the fuzes being to earth, or even insulated, provided a very few yards of conductor exist beyond the fuze. The length of wire which it is necessary to use between the mine and its circuit closer would be quite sufficient for the purpose of effecting ignition by induction. With platinum wire fuses there is no danger whatever of the above happening, nor in the case of high tension fuzes is there so much danger of ignition by induction, when a constant instead of a frictional electric battery is used to generate the current. Another mode of protecting an insulated cable is to place it, as it were, in the core of a hempen cable. In forming the rope on the cable, great care is necessary to prevent any serious amount of torsion, or tension coming on the insulated wire, either of which would most assuredly result in injury to the cable. This form of cable might in connection with obstructions, &c., be of great use, as on account of its closely resembling an ordinary rope, it would be very unlikely to excite suspicion, and so would most probably be cut, the result of which, by previous arrangement, would be an explosion of a mine, or by means of a galvanometer, &c., an indication that the obstructions, &c., were being interfered with.