I am not aware that electricity was used at all in the Confederate war for springing mines on land. Shell cast for this purpose should be used but in an emergency, tin canisters, or other perfectly water-tight cases, will answer. These shells should be one-fourth of an inch thick to one inch, according to size and probable handling in transportation. They should be spherical only instead of a hole for the fuse as in a hollow shot they should have a neck like a bottle, with a cap to screw over, not in the neck. The case should be charged through the neck, and the wires let in through two holes counter sunk diametrically opposite, the counter sinking being for the purpose of receiving pitch or other resinous matter, to keep the water out. The fuse being adjusted to the wires should be held in place by a string through the neck while the wires drawn out taut and sealed within and without. Having proved the fuse, first fill and then drive in the peg. Then fill the space between it and the screw-cap with red lead and screw down so as to make water-tight. Now secure the tails of the wires so that they will not be chafed or bruised, and the mine is ready for transportation. They are general to be used in stone fougasses, the wire being buried at convenient depths and all marks of fougasses and trenches removed as completely as possible. Any number not exceeding twenty-five or thirty may be arranged in a single circuit for the Ebonite; but if the magnetic exploder of Wheatstone be preferred, and the ground be perfectly dry, hundreds may be planted in a latter circuit. The operator may be at any distance from these primas when he explodes them, provided only he has established some mark or point which on being seen by the enemy should serve as a signal. The area of destruction of fougasses properly constructed with a charge of twenty or thirty pounds of powder may be assumed to be that of a circle seventy-five or eighty yards in diameter. Twenty mines would therefore serve for a mile. Several miles may be planted in a night and the assailants may be enticed, or invited out in the morning. Passes before an invading army may be mined in advance and thus if he cannot be destroyed, his progress may be so retarded by dress mines or sham mines as almost literally to dig his way. The power to telegraph through these torpedoes is of little consequence, in as much as there need be but one station and one operator. Using the testing fuse manufactured by Abel and a weak voltaic current, the operator can at any time satisfy himself as to continuity. Thus "bridge" and "gulfs" or "breaks" are not required for the land as they are in sea-mining. Ebonite has the further advantage on land that it takes but a single wire.