A, shews a Torpedo, with the harpoon-line fixed to the centre of its end;
when the line is thus fixed, the tide cannot drive the Torpedo under a
vessel, for the pressure of the current being equal on both sides, it
will hang perpendicular to its suspending box of cork C, Fig. 2, and
remain as at B, where, exploding, it would blow the water perpendicular
to C, and up the side of the ship; the lateral movement of the water from
B to E would give her a sudden cant to one side, but do her no injury.
This has been proved by the following practice.
On the first of October, 1805, captain Siccombe, in a galley with eight
men and his coxswain, placed two Torpedoes in the manner described,
Plate IV, Fig. 2, between the buoy and cable of a French gun-brig, in
Boulogne roads. The tide drove them until they both lay perpendicular
to her sides. When the French saw captain Siccombe advancing without
answering the countersign, they exclaimed that the infernal machines
were coming, and fired a volley of musketry at his boat, but without
touching a man.[C] The moment the French fired, fearing the effect of the
explosions, they all ran aft and were in the greatest confusion. The tide
drove captain Siccombe's boat so far down, that he was obliged to cross
under the brig's stern, where, seeing her men collected, and expecting
another volley, he discharged at them two blunderbusses, each containing
fifteen half-ounce balls[D], and was rowing away, when both Torpedoes
exploded, but, to his astonishment, the brig was not destroyed. On the
same night, lieutenant Payne, of captain Owen's ship _l'Immortality_,
placed two Torpedoes across the bow of another French gun-brig; he
received their fire, had one man wounded, rowed to some distance, and
waited till he saw the explosion of the Torpedoes, which did not appear
to do any injury to the vessel. When captain Siccombe called on me in the
morning and reported these circumstances, I was much at a loss to account
for the brig not being blown up. Defective in the experience which this
failure gave me, I had not reflected, that if the copper case, with the
clockwork and powder, weighed specifically fifteen or twenty pounds
more than water, it would hang like a heavy pendulum to its suspending
cork-box C, and if the coupling line were fixed in the centre of the end,
as at A, Fig. 1, the action of the tide being equal on both sides, would
have no tendency to sheer or drive it from its perpendicular position.
After about half an hour's consideration, I was forcibly impressed with
this error in arrangement, as the real cause of captain Siccombe's and
lieutenant Payne's failure.
[Footnote C: They had got some idea of these machines, from an attempt
which had been made with them against the Boulogne flotilla, in Oct.
1804, called the Catamaran expedition.]
[Footnote D: The report on this attack in the French papers, acknowledged
that the brig had five men killed and eight wounded: this from two
blunderbusses shews that the persons in the vessel attacked have to fear
the small arms of the Torpedo boats.]
I immediately had a large tub made, then filling a copper case with
powder, I screwed on to it the clockwork lock, and tied to it the
pine box C, then suspending the whole Torpedo by a line in the tub
of seawater; the end of the suspending line was tied to one end of a
scale-beam. I then filled the pine box C with cork, until the whole
volume of the Torpedo and box of cork would, when just covered with
water, hold three pounds in equilibrio in the scale on the other end of
the beam. The Torpedo being then three pounds heavier than water, had a
sufficient tendency to sink; and being so balanced, would, while under
water, be easy moved by a slight pressure to either side. Then, instead
of tying the coupling line to the end of the Torpedo, as at A, I tied it
to a bridle, as at B, which presenting the side on an angle to the tide,
the pressure of the current in the direction of the arrow, would cause
the Torpedo to sheer from B to G. This arrangement perfectly succeeded to
sheer the Torpedo from its perpendicular C, and the side of the vessel to
E, near the keel, a position, near which it should be to do execution.
In this situation, the explosion being under the vessel, would have a
great body of water to remove laterally, before it could get out by a
line curving round her side. The water, when acted on in so instantaneous
a manner as by the explosion of one hundred or one hundred and fifty
pounds of powder, does, for the instant, operate like a solid body;
hence the explosion raises the vessel up with a great force, acting on
a small portion of her bottom, which portion giving way, is the same in
effect, as though a high sea had lifted her fifteen or twenty feet, and
let her down on the point of a rock of three or four feet diameter. This,
I believe, accounts for the certain destruction which will follow all
explosions that take place near the keel. In all cases when the explosion
is under water, the action will be perpendicular to the surface, as from
B to C, for in the perpendicular, there are less particles to remove, and
less resistance than in any diagonal, as for example, from B to D.
The French papers, giving an account of the attack of captain
Siccombe and lieutenant Payne, acknowledged that the Torpedoes blew
up along side of the gun-brigs, but gave them only a violent shock
and cant to one side; they spoke of the engines as things of little
consequence and not to be feared. It is now, however, evident, that
they owed the safety of the two brigs to the trifling circumstance of
the Torpedoes not being properly balanced in water, and the coupling
lines not being tied to a bridle, so as to make the Torpedoes sheer
under the bottoms of the brigs.