opportunity of changing the subject, "is meant to illustrate our method
of countermining. You must know that our enemies may sometimes sink
torpedoes at the entrance of their harbours, to prevent our ships of war
entering. Such torpedoes consist usually of casks or cases of
explosives, which are fired either by electric wires, like the
telegraph, when ships are seen to be passing over them, or by _contact_.
That is to say, an enemy's ship entering a harbour runs against
something which sets something else in motion, which explodes the
torpedo and blows it and the ship into what natives of the Green Isle
call smithereens. This is very satisfactory when it happens to an
enemy, but not when it happens to one's-self, therefore when _we_ have
to enter an enemy's harbour we _countermine_. This operation is now
about to be illustrated. The last experiments exhibited the power of
offensive torpedoes. There are several different kinds, such as Mr
Whitehead's fish-torpedo, the Harvey torpedo, and others."

"Dear me," said my mother, with a perplexed air, "I should have thought,
Mr Firebrand, that all torpedoes were offensive."

"By no means; those which are placed at the entrance of harbours and
navigable rivers are defensive. To protect ourselves from the offensive
weapon, we use crinolines."

My mother looked quickly up at her polite young mentor. "You play with
the ignorance of an old woman, sir," she said, with a half-jocular air.

"Indeed I do not, madam, I assure you," returned Firebrand, with much
earnestness. "Every iron-clad is provided with a crinoline, which is a
powerful iron network, hung all round the ship at some distance from
her, like--pardon me--a lady's crinoline, and is intended to intercept
any torpedo that may be discharged against her."

Attention was called, at this point, to the counter-mining experiments.

It may be said, in regard to these, that they can be conducted in
various ways, but always with the same end in view, namely, to destroy
an enemy's mines by exploding others in their midst.

For the sake of illustration, it was supposed that the surrounding
sea-bottom was studded with invisible torpedoes, and that the _Nettle_
was a warship, determined to advance into the enemy's harbour. To
effect this with safety, and in order to clear away the supposed sunken
torpedoes, a counter-torpedo was floated between two empty casks, and
sent off floating in the desired direction by means of