“Dear me, Mr Firebrand, is a popular explanation impossible?”
“Not impossible, madam, but rather difficult. Let me see. Gun-cotton is a chemical compound of the elements which I have just named—a chemical compound, you will observe, not a mechanical mixture, like gunpowder. Hence it explodes more rapidly than the latter, and its power is from three to six times greater.”
My mother looked perplexed. “What is the difference,” she asked, “between a chemical compound and a mechanical mixture?”
Firebrand now in his turn looked perplexed. “Why, madam,” he exclaimed, in modulated desperation, “the ultimate molecules of a mixture are only placed beside each other, so that an atom of gunpowder may be saltpetre, charcoal, or sulphur, dependent on its fellow-atoms for power to act; whereas a chemical compound is such a perfect union of substances, that each ultimate molecule is complete in its definite proportions of the four elements, and therefore an independent little atom.”
“Now, the next experiment,” continued Firebrand, glad to have an 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 the tide. This countermine consisted of an iron cylinder, containing 300 pounds of powder, and was electrically connected with the Nettle. A small charge of gun-cotton was fixed to the suspender that held the torpedo to its casks. When at a safe distance from the ship, this charge was fired. It cut the suspender and let the torpedo sink to the bottom. There it was exploded with terrific violence, as was quickly shown by the mighty fountain of mud, water, and smoke that instantly shot up into the air. It has been proved by experiment that 500 pounds of gun-cotton exploded below water, will destroy all the torpedoes that lie within a radius of 120 yards. It is obvious, therefore, that a warship could advance into the space thus cleared and then send a second countermine ahead of her in the same way. If neither tide, current, nor wind will serve to drift the casks, the operation might be accomplished by a small boat, which could back out of danger after laying each torpedo, and thus, step by step, or shot by shot, the advance could be made in safety through the enemy’s defences.
After this, twelve small charges of gun-cotton were sunk in various directions, each representing a countermine of 500 pounds. These were discharged simultaneously, to demonstrate the possibility of extending the operations over a wide area. These miniature charges were sent down in small nets, and were quite unprotected from the water, so that the gun-cotton was wet when fired.
This fact caught the attention of my mother at once.
“How can it go off when wet?” she exclaimed, turning her bright little eyes in astonishment on her young companion.
“Ha, that is one of the strange peculiarities of gun-cotton,” replied Firebrand, with an amused look; “you don’t require to keep it dry like powder. It is only necessary that there should be one small lump of dry gun-cotton inside the wet stuff, with a detonator in its heart. A detonator, you must know—”
“Oh, I know what a detonator is,” said my mother, quickly.
“Well then,” continued Firebrand, “the exploding of the detonator and the dry disc causes the wet gun-cotton also to go off, as you have seen. Now they are going to exhibit one of the modes of defending harbours. They have sunk four mines, of 300 pounds of gunpowder each, not far from where you see yon black specks floating on the water. The black specks are buoys, called circuit-closers, because they contain a delicate contrivance—a compound of mechanism and galvanism—which, when the buoys are bumped, close the electric circuit and cause the mine to explode. Thus when a ship-of-war sails against one of these circuit-closers, she is immediately blown up.”
“Is not that rather a sneaking way of killing one’s enemies?” asked my mother.
Young Firebrand laughed, and admitted that it was, but pleaded that everything was fair in love and war.
In actual warfare the circuit-closers are placed just over the mines which they are designed to explode, but for safety on this occasion they were placed at a safe distance from their respective mines. A steam-launch was used to bump them, and a prodigious upheaval of water on each explosion showed clearly enough what would have been the fate of an iron-clad if she had been over the mine.
“Oh, shade of Nelson!” I could not help exclaiming, “how shocked you must be if you are permitted to witness such methods of conducting war.”
“Ah, yes!” sighed Firebrand; “the bubble reputation, you see, is being transferred from the cannon’s mouth to the torpedo.”
I made no reply, for my mind reverted to my laboratory in Devonshire, where lay the working-model of the terrible weapon I had spent so much time in perfecting. It seemed strange to me now, that, in the eager pursuit of a scientific object, I had scarcely ever, if at all, reflected on the dire results that the use of my torpedo involved, and I felt as if I were really guilty of the intent to murder. Just before leaving home I had charged my model, which was quite a large one, capable of holding about 50 pounds of dynamite, in the hope that I might prevail on the First Lord of the Admiralty and some of his colleagues to come down and see it actually fired. I now resolved to throw the dynamite into the sea, break up my model, and have done with explosives for ever.
While my mind was running on this, I was startled by an explosion close alongside. On turning towards the side of the ship, I found that it was caused by the rending of a huge iron chain, the links of which were more than one and a quarter inch in thickness. This powerful cable, which could have held an iron-clad, was snapped in twain like a piece of thread by the explosion against it of only two