d in a river channel, being fired by electricity when the
vessel came over them. The second kind was the floating or Harvey's
torpedo, consisting of a long narrow, but deep wooden case from 44 to 60
inches in length, which contained 30 to 80 pounds of gunpowder, inside a
copper lining. It had two levers projecting on the outside, which, on
striking an object, set off the explosive inside. This torpedo was used
in two ways: the first by setting it adrift on a river, or where there
was a well-marked current setting towards the enemy's ships, when the
current carried it to its destination; the other way was by towing it at
night, by means of a long line, across the bows of an enemy's ship; it
exploded whenever it came in contact with the ship.

The third kind of torpedo was practically a Harvey's torpedo attached to
a long boom, or pole, about 28 feet long. This was carried at the
gunwale of a fast steam launch at night; on nearing the enemy's ship
this boom was pushed forward so as to bring the torpedo ten feet below
the surface and well in advance of the boat. The torpedo exploded when
it struck the ship, and to prevent the torpedo-boat from being sunk by
the huge wave raised by the explosion, it had to be covered in front by
a shield.

The experiences of the two wars already mentioned showed the difficulty
of dealing with torpedo boats at night, and "search lights" are now
installed on all modern warships. These consist of an electric arc lamp
of 25,000 candle-power, combined with a reflector, which concentrates
the light so that it brilliantly lights up objects at a great distance.
Torpedo boats can be readily discovered when a mile or more distant and,
at the same distance from the light, the rays are so powerful that a
newspaper can be read with the greatest ease.

Torpedo attack, however, has been revolutionised by the invention of
"Whitehead's torpedo," which can be used from a distance. In shape it
is exactly like a huge cigar, 12 to 18 inches in diameter, and 6 to 10
feet long. At the head is the explosive; behind this is a reservoir
containing air compressed to an enormous pressure, which drives engines
contained in a third compartment, and which in their turn work a screw
propeller at the back of the torpedo. There is also mechanism which
automatically adjusts the depth at which the torpedo travels below the
water, and other mechanism which ensures that it will keep going in the
direction in which it