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.

Forts may be protected against assault and your own rifle pits from
occupation by an enemy simply by a proper distribution of these new
engines of war. They may be planted line within line and one row above
another, and so arranged that volcanoes can be sprung at will under the
feet of assaulting columns. And these improvements and discoveries
enable the engineer at small cost, and short notice effectually to
defend any roadstead, or block any river, harbour or pass against the
land and naval forces of an enemy without in the least