crystals were placed in pots, and the heat from the furnace would distil the sulphuric acid. The operation was successfully completed, and on the 20th of May, twelve days after commencing it, the engineer was the possessor of the agent which later he hoped to use in so many different ways.
Now, why did he wish for this agent? Simply to produce azotic acid; and that was easy, since saltpeter, attacked by sulphuric acid, gives azotic, or nitric, acid by distillation.
But, after all, how was he going to employ this azotic acid? His companions were still ignorant of this, for he had not informed them of the result at which he aimed.
However, the engineer had nearly accomplished his purpose, and by a last operation he would procure the substance which had given so much trouble.
Taking some azotic acid, he mixed it with glycerine, which had been previously concentrated by evaporation, subjected to the water-bath, and he obtained, without even employing a refrigerant mixture, several pints of an oily yellow mixture.
This last operation Cyrus Harding had made alone, in a retired place, at a distance from the Chimneys, for he feared the danger of an explosion, and when he showed a bottle of this liquid to his friends, he contented himself with saying,—
“Here is nitro-glycerine!”
It was really this terrible production, of which the explosive power is perhaps tenfold that of ordinary powder, and which has already caused so many accidents. However, since a way has been found to transform it into dynamite, that is to say, to mix with it some solid substance, clay or sugar, porous enough to hold it, the dangerous liquid has been used with some security. But dynamite was not yet known at the time when the settlers worked on Lincoln Island.
“And is it that liquid that is going to blow up our rocks?” said Pencroft incredulously.
“Yes, my friend,” replied the engineer, “and this nitro-glycerine will produce so much the more effect, as the granite is extremely hard, and will oppose a greater resistance to the explosion.”
“And when shall we see this, captain?”
“To-morrow, as soon as we have dug a hole for the mine, replied the engineer.”
The next day, the 21st of May, at daybreak, the miners went to the point which formed the eastern shore of Lake Grant, and was only five hundred feet from the coast. At this place, the plateau inclined downwards from the waters, which were only restrained by their granite case. Therefore, if this case was broken, the water would escape by the opening and form a stream, which, flowing over the inclined surface of the plateau, would rush on to the beach. Consequently, the level of the lake would be greatly lowered, and the opening where the water escaped would be exposed, which was their final aim.
Under the engineer’s directions, Pencroft, armed with a pickaxe, which he handled skillfully and vigorously, attacked the granite. The hole was made on the point of the shore, slanting, so that it should meet a much lower level than that of the water of the lake. In this way the explosive force, by scattering the rock, would open a large place for the water to rush out.
The work took some time, for the engineer, wishing to produce a great effect, intended to devote not less than seven quarts of nitro-glycerine to the operation. But Pencroft, relieved by Neb, did so well, that towards four o’clock in the evening, the mine was finished.
Now the question of setting fire to the explosive substance was raised. Generally, nitro-glycerine is ignited by caps of fulminate, which in bursting cause the explosion. A shock is therefore needed to produce the explosion, for, simply lighted, this substance would burn without exploding.
Cyrus Harding could certainly have fabricated a percussion cap. In default of fulminate, he could easily obtain a substance similar to guncotton, since he had azotic acid at his disposal. This substance, pressed in a cartridge, and introduced among the nitro-glycerine, would burst by means of a fuse, and cause the explosion.
But Cyrus Harding knew that nitro-glycerine would explode by a shock. He resolved to employ this means, and try another way, if this did not succeed.
In fact, the blow of a hammer on a few drops of nitro-glycerine, spread out on a hard surface, was enough to create an explosion. But the operator could not be there to give the blow, without becoming a victim to the operation. Harding, therefore, thought of suspending a mass of iron, weighing several pounds, by means of a fiber, to an upright just above the mine. Another long fiber, previously impregnated with sulphur, was attached to the middle of the first, by one end, while the other lay on the ground several feet distant from the mine. The second fiber being set on fire, it would burn till it reached the first. This catching fire in its turn, would break, and the mass of iron would fall on the nitro-glycerine. This apparatus being then arranged, the engineer, after having sent his companions to a distance, filled the hole, so that the nitro-glycerine was on a level with the opening; then he threw a few drops of it on the surface of the rock, above which the mass of iron was already suspended.
This done, Harding lit the end of the sulphured fiber, and leaving the place, he returned with his companions to the Chimneys.
The fiber was intended to burn five and twenty minutes, and, in fact, five and twenty minutes afterwards a most tremendous explosion was heard. The island appeared to tremble to its very foundation. Stones were projected in the air as if by the eruption of a volcano. The shock produced by the displacing of the air was such, that the rocks of the Chimneys shook. The settlers, although they were more than two miles from the mine, were thrown on the ground.
They rose, climbed the plateau, and ran towards the place where the bank of the lake must have been shattered by the explosion.
A cheer escaped them! A large rent was seen in the granite! A rapid stream of water rushed foaming across the plateau and dashed down a height of three hundred feet on to the beach!
Chapter 18
Cyrus Harding’s project had succeeded, but, according to his usual habit he showed no satisfaction; with closed lips and a fixed look, he remained motionless. Herbert was in ecstasies, Neb bounded with joy, Pencroft nodded his great head, murmuring these words,—
“Come, our engineer gets on capitally!”
The nitro-glycerine had indeed acted powerfully. The opening which it had made was so large that the volume of water which escaped through this new outlet was at least treble that which before passed through the old one. The result was, that a short time after the operation the level of the lake would be lowered two feet, or more.
The settlers went to the Chimneys to take some pickaxes, iron-tipped spears, string made of fibers, flint and steel; they then returned to the plateau, Top accompanying them.
On the way the sailor could not help saying to the engineer,—
“Don’t you think, captain, that by means of that charming liquid you have made, one could blow up the whole of our island?”
“Without any doubt, the island, continents, and the world itself,” replied the engineer. “It is only a question of quantity.”
“Then could you not use this nitro-glycerine for loading firearms?” asked the sailor.
“No, Pencroft; for it is too explosive a substance. But it would be easy to make some guncotton, or even ordinary powder, as we have azotic acid, saltpeter, sulphur, and coal. Unhappily, it is the guns which we have not got.
“Oh, captain,” replied the sailor, “with a little determination—”
Pencroft had erased the word “impossible” from the dictionary of Lincoln Island.
The settlers, having arrived at Prospect Heights, went immediately towards that point of the lake near which was the old opening now uncovered. This outlet had now become practicable, since the water no longer rushed through