# Works of Jules Verne/The Mysterious Island/Dropped from the Clouds/Chapter 17

CHAPTER XVII MAKING A CATARACT
The next day, the 7th of May, Harding and Gideon Spilett, leaving Neb to prepare breakfast, climbed Prospect Heights, whilst Herbert and Pencroft ascended by the river, to renew their store of wood.
The engineer and the reporter soon reached the little beach on which the dugong had been stranded. Already flocks of birds had attacked the mass of flesh, and had to be driven away with stones, for Cyrus wished to keep the fat for the use of the colony. As to the animal's flesh, it would furnish excellent food, for in the islands of the Malay archipelago and elsewhere, it is especially reserved for the table of the native princes. But that was Neb's affair.
​At this moment Cyrus Harding had other thoughts. He was much interested in the incident of the day before. He wished to penetrate the mystery of that submarine combat, and to ascertain what monster could have given the dugong so strange a wound. He remained at the edge of the lake, looking, observing; but nothing appeared under the tranquil waters which sparkled in the first rays of the rising sun.
At the beach, on which lay the body of the dugong, the water was tolerably shallow, but from this point the bottom of the lake sloped gradually, and it was probable that the depth was considerable in the center. The lake might be considered as a large center basin, which was filled by the water from the Red Creek.
"Well, Cyrus," said the reporter, "there seems to be nothing suspicious in this water."
"No, my dear Spilett," replied the engineer, "and I really do not know how to account for the incident of yesterday."
"I acknowledge," returned Spilett, "that the wound given to this creature is, at least, very strange, and I cannot explain either how Top was so vigorously cast up out of the water. One would have thought that a powerful arm hurled him up, and that the same arm with a dagger killed the dugong!"
"Yes," replied the engineer, who had become thoughtful; "there is something there that I cannot understand. But do you better understand either, my dear Spilett, in what way I was saved myself—how I was drawn from the waves, and carried to the downs? No! Is it not true? Now, I feel sure that there is some mystery there, which, doubtless, we shall discover some day. Let us observe, but do not dwell on these singular incidents before our companions. Let us keep our remarks to ourselves, and continue our work."
It will be remembered that the engineer had not as yet been able to discover the place where the surplus water escaped, but he knew it must exist somewhere. He was much surprised to see a strong current at this place. By throwing in some bits of wood he found that it set towards the southern angle. He followed the current, and arrived at the south point of the lake.
​There was there a sort of depression in the water, as if it was suddenly lost in some fissure in the ground.
Cyrus Harding listened; placing his ear to the level of the lake, he very distinctly heard the noise of a subterranean fall.
"There," said he, rising, "is the discharge of the water; there, doubtless, by a passage in the granite cliff, it joins the sea, through cavities which we can use to our profit. Well, I can find it!"
The engineer cut a long branch, stripped it of its leaves, and, plunging it into the angle between the two banks, he found that there was a large hole one foot only beneath the surface of the water. This hole was the opening so long looked for in vain, and the force of the current was such that the branch was torn from the engineer's hands and disappeared.
"There is no doubt about it now," repeated Harding. "There is the outlet, and I will lay it open to view!"
"How?" asked Gideon Spilett.
"By lowering the level of the lake water three feet."
"And how will you lower the level?"
"By opening another outlet larger than this."
"At what place, Cyrus?"
"At the part of the bank nearest the coast."
"But it is a mass of granite!" observed Spilett.
"Well," replied Cyrus Harding, "I will blow up the granite, and the water escaping, will subside, so as to lay bare this opening———"
"And make a waterfall, by falling on to the beach," added the reporter.
"A fall that we shall make use of!" replied Cyrus.
"Come, come!"
The engineer hurried away his companion, whose confidence in Harding was such that he did not doubt the enterprise would succeed. And yet, how was this granite wall to be opened without powder, and with imperfect instruments? Was not this work upon which the engineer was so bent above their strength?
When Harding and the reporter entered the Chimneys, Herbert and Pencroft were unloading their raft of wood. "The woodmen have just finished, captain," said the sailor, laughing, "and when you want masons———"
​"Masons,—no, but chemists," replied the engineer.
"Yes," added the reporter, "we are going to blow up the island———"
"Blow up the island?" cried Pencroft.
"Part of it, at least," replied Spilett.
"Listen to me, my friends," said the engineer. And he made known to them the result of his observations.
According to him, a cavity, more or less considerable, must exist in the mass of granite which supported Prospect Heights, and he intended to pentrate into it. To do this, the opening through which the water rushed must first be cleared, and the level lowered by making a larger outlet. Therefore an explosive substance must be manufactured, which would make a deep trench in some other part of the shore. This was what Harding was going to attempt with the minerals which nature placed at his disposal.
It is useless to say with what enthusiasm all, especially Pencroft, received this project. To employ great means, open the granite, create a cascade, that suited the sailor. And he would just as soon be a chemist as a mason or bootmaker, since the engineer wanted chemicals. He would be all that they liked, "even a professor of dancing and deportment," said he to Neb, if that was ever necessary.
Neb and Pencroft were first of all told to extract the grease from the dugong, and to keep the flesh for food. Such perfect confidence had they in the engineer, that they set out directly, without even asking a question. A few minutes after them, Cyrus Harding, Herbert, and Gideon Spilett, dragging the hurdle, went towards the vein of coals, where those schistose pyrites abound which are met with in the most recent transition soil, and of which Harding had already found a specimen. All the day being employed in carrying a quantity of these stones to the Chimneys, by evening they had several tons.
The next day, the 8th of May, the engineer began his manipulations. These schistose pyrites being composed principally of coal, flint, alumina, and sulphuret of iron—the latter in excess—it was necessary to separate the sulphuret of iron, and transform it into sulphate as rapidly as possible. The sulphate obtained, the sulphuric acid could then be extracted.
​This was the object to be attained. Sulphuric acid is one of the agents the most frequently employed, and the manufacturing importance of a nation can be measured by the consumption which is made of it. This acid would later be of great use to the settlers, in the manufacturing of candles, tanning skins, etc., but this time the engineer reserved it for another use.
Cyrus Harding chose, behind the Chimneys, a site where the ground was perfectly level. On this ground he placed a layer of branches and chopped wood, on which were piled some pieces of schistose pyrites, buttressed one against the other, the whole being covered with a thin layer of pyrites, previously reduced to the size of a nut.
This done, they set fire to the wood, the heat was communicated to the schist, which soon kindled, since it contains coal and sulphur. Then new layers of bruised pyrites were arranged so as to form an immense heap, the exterior of which was covered with earth and grass, several air-holes being left, as if it was a stack of wood which was to be carbonized to make charcoal.
They then left the transformation to complete itself, for it would take ten or twelve days for the sulphuret of iron to be changed into sulphate of iron and the alumina into sulphate of alumina, two equally soluble substances, the others, flint, burnt coal, and cinders, not being so. While this chemical work was going on, Cyrus Harding proceeded with other operations, which were pursued with more than zeal,—it was eagerness.
Neb and Pencroft had taken away the fat from the dugong, and placed it in large earthen pots. It was then necessary to separate the glycerine from the fat by saponifying it. Now, to obtain this result, it had to be treated either with soda or lime. In fact, one or other of these substances, after having attacked the fat, would form a soap by separating the glycerine, and it was just this glycerine which the engineer wished to obtain. There was no want of lime, only treatment by lime would give calcareous soap, insoluble, and consequently useless, whilst treatment by soda would furnish, on the contrary, a soluble soap, which could be put to domestic use. Now, a practical man, like Cyrus Harding, would rather try to obtain soda. Was this difficult? No; for marine plants abounded on the ​shore, glass-wort, ficoides, and all those fucaceæ which form wrack. A large quantity of these plants was collected, first dried, then burnt in holes in the open air. The combustion of these plants was kept up for several days, and the result was a compact gray mass, which has been long known under the name of "natural soda." This obtained, the engineer treated the fat with soda, which gave both a soluble soap and that neutral substance glycerine.
But this was not all. Cyrus Harding still needed, in view of his future preparation, another substance, azote of potash, which is better known under the name of salt of nitre, or of saltpetre. He could have manufactured this substance by treating the carbonate of potash, which would be easily extracted from the cinders of the vegetables, by azotic acid. But this acid was wanting, and he would have been in some difficulty, if nature had not happily furnished the saltpetre, without giving them any other trouble than that of picking it up. Herbert found a vein of it at the foot of Mount Franklin, and they had nothing to do but purify this salt
These different works lasted a week. They were finished before the transformation of the sulphuret into sulphate of iron had been accomplished. During the following days the settlers had time to construct a furnace of bricks of a particular arrangement, to serve for the distillation of the sulphate of iron when it had been obtained. All this was finished about the i8th of May, nearly at the time when the chemical transformation terminated. Gideon Spilett, Herbert, Neb, and Pencroft, skillfully directed by the engineer, had become most clever workmen. Before all masters, necessity is the one most listened to, and who teaches the best.
When the heap of pyrites had been entirely reduced by fire, the result of the operation, consisting of sulphate of iron, sulphate of alumina, flint, remains of coal, and cinders, was placed in a basin full of water. They stirred this mixture, let it settle, then decanted it, and obtained a clear liquid, containing in solution sulphate of iron and sulphate of alumina, the other matters remaining solid since they are insoluble. Lastly, this liquid being partly evaporated, crystals of sulphate of iron were deposited, and the not ​evaporated liquid, which contained the sulphate of alumina, was thrown away.
Cyrus Harding had now at his disposal a large quantity of these sulphate of iron crystals, from which the sulphuric acid had to be extracted. The making of sulphuric acid is a very expensive manufacture. Considerable works are necessary—a special set of tools, an apparatus of platina, leaden chambers, unassailable by the acid, and in which the transformation is performed, etc. The engineer had none of these at his disposal, but he knew that, in Bohemia especially, sulphuric acid is manufactured by very simple means, which have also the advantage of producing it to a superior degree of concentration. It is thus that the acid known under the name of Nordhausen acid is made.
To obtain sulphuric acid, Cyrus Harding had only one operation to make, to calcine the sulphate of iron crystals in a close vase, so that the sulphuric acid should distill in vapor, which vapor, by condensation, would produce the acid.
The crystals were placed in pots, and the heat from the furnace would distill the sulphuric acid. The operation was successfully completed, and on the 2Oth 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 saltpetre, attacked by sulphuric acid, gives this 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 more security. But dynamite was not yet known at the time when the settlers worked in 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 nitroglycerine 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 2ist 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 direction, Pencroft, armed with a pickax, 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 Pen​croft, 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 amorces 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 would certainly have been able to fabricate an amorce. In default of fulminate, he could easily obtain a substance similar to gun-cotton, since he had azotic acid at his disposal. This substance, pressed in a cartridge, and introduced amongst the nitro-glycerine, would burst by means of a match, 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 nitroglycerine, 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, whilst 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!
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