_Represents a clockwork Torpedo, as prepared for the attack of a vessel
while at anchor or under sail, by harpooning her in the larboard and
starboard bow._
B is a copper case to contain one hundred or more pounds of powder; C
a cork cushion to give the whole Torpedo such a buoyancy, that it will
be only from two to three pounds heavier than salt water. To ascertain
such weight, when it is charged with powder and the lock screwed on, it
is put into a large tub of sea water. C is to have fifteen or twenty
inch-holes bored in its sides and top, to let the water rush in and the
air out, otherwise, the air would prevent its immediately sinking. A is
a cylindric brass box, about seven inches diameter and two inches deep,
in which there is a gun-lock with a barrel two inches long, to receive
a charge of powder and a wad, which charge is fired into the powder of
the case B. In the brass box A there is also a piece of clockwork moved
by a spring, which being wound up and set, will let the lock strike fire
in any number of minutes which may be determined within one hour. K is
a small line fixed to a pin, which pin holds the clockwork inactive;
the instant the pin is withdrawn the clockwork begins to move, and the
explosion will take place in one, two, three, or any number of minutes
for which it has been set; the whole is so made as to be perfectly tight
and keep out the water, although under a pressure of twenty-five or
thirty perpendicular feet. D is a pine box two feet long, six or eight
inches square, filled with cork; it is ten or fifteen pounds lighter
than water, and floats on the surface; the line from it to the Torpedo
is the suspending line, which must be of a length in proportion to the
estimated draft of water of the vessel to be attacked; vessels of a
certain number of guns usually draw within a few feet of the same draft
of water; the suspending line should be from four to eight feet longer
than the greatest draft of the vessel, that it may bend round the curve
of her side, and lay the Torpedo near her keel. From the Torpedo and the
float D, two lines, each twenty feet long, are united at E, from thence
one line goes to the harpoon, the total length of the line from the
Torpedo to the harpoon being about fifty feet, according to the length
of the vessel to be attacked, will, when the ship is harpooned in the
bow, bring the Torpedo under her bottom near midship. See the harpoon.
It is a round piece of iron, half an inch diameter and two feet long,
the butt one inch diameter, the exact calibre of the harpoon-gun; in the
head of the harpoon there is an eye, the point six inches long is barbed,
the line of the Torpedo is spliced into the eye of the harpoon, a small
iron or tough copper link runs on the shaft of the harpoon, to the link
the Torpedo-line is also tied, and at such a distance, that when the
harpoon is in the gun it will form a loop as at H, but when fired, the
link will slide along to the butt of the harpoon, and, holding the rope
and harpoon parallel to each other, the rope will act like a tail or rod
to a rocket, and guide it straight; without this precaution, the butt of
the harpoon would turn foremost, and make a very uncertain shot. F is the
harpoon-gun, made strong, and to work on a swivel in a stanchion fixed
in the stern-sheets of a boat. My experience with this kind of harpoon
and gun, is, that I have harpooned a target of six feet square fifteen
or twenty times, at the distance of from thirty to fifty feet, never
missing, and always driving the barbed point through three inch boards up
to the eye, which practice was so satisfactory, that I did not consider
it necessary to repeat it. The object of harpooning a vessel on the
larboard and starboard bow, is, to fix one end of the Torpedo-line, then,
if the ship be under sail, her action through the water will draw the
Torpedo under her; if she be at anchor, the tide will drive it under her,
where, at the expiration of the time for which the clockwork was set, the
explosion will destroy her.
This being the kind of Torpedo and clockwork by which the _Dorothea_
in Walmer roads, and the brig in New-York harbour were blown up, and
the harpoon having succeeded to fix the line to the target, these two
experiments shall be combined, and the mode of practice, with the
prospect of success and risque to the assailants, examined.
[Illustration: PLATE IV.
_Fig. 1._
_Fig. 2._]