<h2><SPAN name="XVII" id="XVII"></SPAN>CHAPTER XVII</h2>
<p class="letter">
A VISIT TO THE LAKE—THE DIRECTION OF THE CURRENT—THE PROSPECTS OF
CYRUS SMITH—THE DUGONG FAT—THE USE OF THE SCHISTOUS
LIMESTONE—THE SULPHATE OF IRON—HOW GLYCERINE IS
MADE—SOAP—SALTPETRE—SULPHURIC ACID—NITRIC
ACID—THE NEW OUTLET.</p>
<p>The next day, the 7th of May, Smith and Spilett, leaving Neb to prepare the
breakfast, climbed the plateau, while Herbert and Pencroff went after a fresh
supply of wood.</p>
<p>The engineer and the reporter soon arrived, at the little beach where the
dugong lay stranded. Already flocks of birds had gathered about the carcass,
and it was necessary to drive them off with stones, as the engineer wished to
preserve the fat for the use of the colony. As to the flesh of the dugong, it
would undoubtedly furnish excellent food, as in certain portions of the Malay
archipelago it is reserved for the table of the native princes. But it was
Neb’s affair to look after that.</p>
<p>Just now, Cyrus Smith was thinking of other things. The incident of the day
before was constantly presenting itself. He wanted to solve the mystery of that
unseen combat, and to know what congener of the mastodons or other marine
monster had given the dugong this strange wound.</p>
<p>He stood upon the border of the lake, looking upon its tranquil surface
sparkling under the rays of the rising sun. From the little beach where the
dugong lay, the waters deepened slowly towards the centre, and the lake might
be likened to a large basin, filled by the supply from Red Creek.</p>
<p>“Well, Cyrus,” questioned the reporter, “I don’t see
anything suspicious in this?”</p>
<p>“No, my dear fellow, and I am at a loss how to explain yesterday’s
affair.”</p>
<p>“The wound on this beast is strange enough, and I can’t understand
how Top could have been thrown out of the water in that way. One would suppose
that it had been done by a strong arm, and that that same arm, wielding a
poignard, had given the dugong his death-wound.”</p>
<p>“It would seem so,” answered the engineer, who had become
thoughtful. “There is something here which I cannot understand. But
neither can we explain how I myself was saved; how I was snatched from the
waves and borne to the downs. Therefore, I am sure there is some mystery which
we will some day discover. In the mean time, let us take care not to discuss
these singular incidents before our companions, but keep our thoughts for each
other, and continue our work.”</p>
<p>It will be remembered that Smith had not yet discovered what became of the
surplus water of the lake, and as there was no indication of its ever
overflowing, an outlet must exist somewhere. He was surprised, therefore, on
noticing a slight current just at this place. Throwing in some leaves and bits
of wood, and observing their drift, he followed this current, which brought him
to the southern end of the lake. Here he detected a slight depression in the
waters, as if they were suddenly lost in some opening below.</p>
<p>Smith listened, placing his ear to the surface of the lake, and distinctly
heard the sound of a subterranean fall.</p>
<p>“It is there,” said he, rising, “there that the water is
discharged, there, doubtless, through a passage in the massive granite that it
goes to join the sea, through cavities which we will be able to utilize to our
profit! Well! I will find out!”</p>
<p>The engineer cut a long branch, stripped off its leaves, and, plunging it down
at the angle of the two banks, he found that there was a large open hole a foot
below the surface. This was the long-sought-for outlet, and such was the force
of the current that the branch was snatched from his hands and disappeared.</p>
<p>“There can be no doubt of it now,” repeated the engineer. “It
is the mouth of the outlet, and I am going to work to uncover it.</p>
<p>“How?” inquired Spilett.</p>
<p>“By lowering the lake three feet.”</p>
<p>“And how will you do that?”</p>
<p>“By opening another vent larger than this.”</p>
<p>“Whereabouts, Cyrus?”</p>
<p>“Where the bank is nearest the coast.”</p>
<p>“But it is a granite wall,” exclaimed Spilett,</p>
<p>“Very well,” replied Smith. “I will blow up the wall, and the
waters, escaping, will subside so as to discover the orifice—”</p>
<p>“And will make a waterfall at the cliff,” added the reporter.</p>
<p>“A fall that we will make use of!” answered Cyrus. “Come,
come!”</p>
<p>The engineer hurried off his companion, whose confidence in Smith was such that
he doubted not the success of the undertaking. And yet, this wall of granite,
how would they begin: how, without powder, with but imperfect tools, could they
blast the rock? Had not the engineer undertaken a work beyond his skill to
accomplish?</p>
<p>When Smith and the reporter re-entered the Chimneys, they found Herbert and
Pencroff occupied in unloading their raft.</p>
<p>“The wood-choppers have finished, sir,” said the sailor, laughing,
“and when you want masons—”</p>
<p>“Not masons, but chemists,” interrupted the engineer.</p>
<p>“Yes,” added Spilett, “we are going to blow up the
island.”</p>
<p>“Blow up the island?” cried the sailor.</p>
<p>“A part of it, at least,” answered the reporter.</p>
<p>“Listen to me, my friends,” said the engineer, who thereupon made
known the result of his observations. His theory was, that a cavity, more or
less considerable, existed in the mass of granite which upheld Prospect
Plateau, and he undertook to penetrate to it. To do this, it was first
necessary to free the present opening, in other words to lower the level of the
lake by giving the water a larger issue. To do this they must manufacture an
explosive with which to make a drain in another part of the bank. It was this
Smith was going to attempt to do, with the minerals Nature had placed at his
disposal.</p>
<p>All entered into the proposal with enthusiasm. Neb and Pencroff were at once
detailed to extract the fat from the dugong and to preserve the flesh for food;
and soon after their departure the others, carrying the hurdle, went up the
shore to the vein of coal, where were to be found the schistous pyrites of
which Smith had procured a specimen.</p>
<p>The whole day was employed in bringing a quantity of these pyrites to the
Chimneys, and by evening they had several tons.</p>
<p>On the next day, the 8th of May, the engineer began his manipulations. The
schistous pyrites were principally composed of carbon, of silica, of alumina,
and sulphuret of iron,—these were in excess,—it was necessary to
separate the sulphuret and change it into sulphate by the quickest means. The
sulphate obtained, they would extract the Sulphuric acid, which was what they
wanted.</p>
<p>Sulphuric acid is one of the agents in most general use, and the industrial
importance of a nation can be measured by its consumption. In the future this
acid would be of use to the colonists in making candles, tanning skins, etc.,
but at present the engineer reserved it for another purpose.</p>
<p>Smith chose, behind the Chimneys, a place upon which the earth was carefully
levelled. On this he made a pile of branches and cut wood, on which were placed
pieces of schistous pyrites leaning against each other, and then all was
covered over with a thin layer of pyrites previously reduced to the size of
nuts.</p>
<p>This done, they set the wood on, fire, which in turn inflamed the schist, as it
contained carbon and sulphur. Then new layers of pyrites were arranged so as to
form an immense heap, surrounded with earth, and grass, with air-holes left
here and there, just as is done in reducing a pile of wood to charcoal.</p>
<p>Then they left the transformation to complete itself. It would take ten or
twelve days for the sulphuret of iron and the alumina to change into sulphates,
which substances were equally soluble; the others—silica, burnt carbon,
and cinders—were not so.</p>
<p>While this chemical process was accomplishing itself, Smith employed his
companions upon other branches of the work, which they undertook with the
utmost zeal.</p>
<p>Neb and Pencroff had taken the fat from the dugong, which had been placed in
large earthen jars. It was necessary to separate the glycerine from this fat by
saponifying it. It was sufficient, in order to do this, to treat it with chalk
or soda. Chalk was not wanting, but by this treatment the soap would be
calcareous and useless, while by using soda, a soluble soap, which could be
employed for domestic purposes, would be the result. Cyrus Smith, being a
practical man, preferred to try to get the soda. Was this difficult? No, since
many kinds of marine plants abounded on the shore, and all those fucaceæ which
form wrack. They therefore gathered a great quantity of these seaweed, which
were first dried, and, afterwards, burnt in trenches in the open air. The
combustion of these plants was continued for many days, so that the heat
penetrated throughout, and the result was the greyish compact mass, long known
as “natural soda.”</p>
<p>This accomplished, the engineer treated the fat with the soda, which gave both
a soluble soap and the neutral substance, glycerine.</p>
<p>But this was not all. Smith wanted, in view of his future operations, another
substance, nitrate of potash, better known as saltpetre.</p>
<p>He could make this by treating carbonate of potash, which is easily extracted
from vegetable ashes, with nitric acid. But this acid, which was precisely what
he wanted in order to complete his undertaking successfully, he did not have.
Fortunately, in this emergency, Nature furnished him with saltpetre, without
any labor other than picking it up. Herbert had found a vein of this mineral at
the foot of Mount Franklin, and all they had to do was to purify the salt.</p>
<p>These different undertakings, which occupied eight days, were finished before
the sulphate of iron was ready. During the interval the colonists made some
refractory pottery in plastic clay, and constructed a brick furnace of a
peculiar shape, in which to distil the sulphate of iron. All was finished on
the 18th of May, the very day the chemical work was completed.</p>
<p>The result of this latter operation, consisting of sulphate of iron, sulphate
of alumina, silica, and a residue of charcoal and cinders, was placed, in a
basin full of water. Having stirred up the mixture, they let it settle, and at
length poured off a clear liquid holding the sulphates of iron and alumina in
solution. Finally, this liquid was partly evaporated, the sulphate of iron
crystalized, and the mother-water was thrown away.</p>
<p>Smith had now a quantity of crystals, from which the sulphuric acid was to be
extracted.</p>
<p>In commerce this acid is manufactured in large quantities and by elaborate
processes. The engineer had no such means at his command, but he knew that in
Bohemia an acid known as Nordhausen is made by simpler means, which has,
moreover, the advantage of being non-concentrated. For obtaining the acid in
this way, all the engineer had to do was to calcinize the crystals in a closed
jar in such a manner that the sulphuric acid distilled in vapor, which would in
turn produce the acid by condensation.</p>
<p>It was for this that the refractory jars and the furnace had been made. The
operation was a success; and on the 20th of May, twelve days after having
begun, Smith was the possessor of the agent which he expected to use later in
different ways.</p>
<p>What did he want with it now? Simply to produce nitric acid, which was
perfectly easy, since the saltpetre, attacked by the sulphuric acid, would give
it by distillation.</p>
<p>But how would he use this acid? None of the others knew, as he had spoken no
word on the subject.</p>
<p>The work approached completion, and one more operation would procure the
substance which had required all this labor. The engineer mixed the nitric acid
with the glycerine, which latter had been previously concentrated by
evaporation in a water-bath, and without employing any freezing mixture,
obtained many pints of an oily yellow liquid.</p>
<p>This last operation Smith had conducted alone, at some distance from the
Chimneys, as he feared an explosion, and when he returned, with a flagon of
this liquid, to his friends, he simply said:—“Here is some
nitro-glycerine!”</p>
<p>It was, in truth, that terrible product, whose explosive power is, perhaps, ten
times as great as that of gunpowder, and which has caused so many accidents!
Although, since means have been found of transforming it into dynamite, that
is, of mixing it with clay or sugar or some solid substance sufficiently porous
to hold it, the dangerous liquid can be used with more safety. But dynamite was
not known when the colonists were at work on Lincoln Island.</p>
<p>“And is that stuff going to blow up the rocks?” asked Pencroff,
incredulously.</p>
<p>“Yes, my friend,” answered the engineer, “and it will do all
the better since the granite is very hard and will oppose more resistance to
the explosion.”</p>
<p>“And when will we see all this, sir?”</p>
<p>“To-morrow,” when we have drilled a hole,” answered the
engineer.</p>
<p>Early the next morning, the 21st of May, the miners betook themselves to a
point which formed the east bank of Lake Grant, not more than 500 feet from the
coast. At this place the plateau was lower than the lake, which was upheld by
the coping of granite. It was plain that could they break this the waters would
escape by this vent, and, forming a stream, flow over the inclined surface of
the plateau, and be precipitated in a waterfall over the cliff on to the shore.
Consequently, there would be a general lowering of the lake, and the orifice of
the water would be uncovered—this was to be the result.</p>
<p>The coping must be broken. Pencroff, directed by the engineer, attacked its
outer facing vigorously. The hole which he made with his pick began under a
horizontal edge of the bank, and penetrated obliquely so as to reach a level
lower than the lake’s surface. Thus the blowing up of the rocks would
permit the water to escape freely and consequently lower the lake sufficiently.</p>
<p>The work was tedious, as the engineer, wishing to produce a violent shock, had
determined to use not less than two gallons of nitro-glycerine in the
operation. But Pencroff and Neb, taking turns at the work, did so well, that by
4 o’clock in the afternoon it was achieved.</p>
<p>Now came the question of igniting the explosive. Ordinarily, nitro-glycerine is
ignited by the explosion of fulminated caps, as, if lighted without percussion,
this substance burns and does not explode.</p>
<p>Smith could doubtless make a cap. Lacking fulminate, he could easily obtain a
substance analogous to gun-cotton, since he had nitric acid at hand. This
substance pressed in a cartridge, and introduced into the nitro-glycerine,
could be lighted with a slow match, and produce the explosion.</p>
<p>But Smith knew that their liquid had the property of exploding under a blow. He
determined, therefore, to make use of this property, reserving the other means
in case this experiment failed.</p>
<p>The blow of a hammer upon some drops of the substance spread on a hard stone,
suffices to provoke an explosion. But no one could give those blows without
being a victim to the operation. Smith’s idea was to suspend a heavy mass
of iron by means of a vegetable fibre to an upright post, so as to have the
iron hang directly over the hole. Another long fibre, previously soaked in
sulphur, was to be fastened to the middle of the first and laid along the
ground many feet from this excavation. The fire was to be applied to this
second fibre, it would burn till it reached the first and set it on fire, then
the latter would break and the iron be precipitated upon the nitro-glycerine.</p>
<p>The apparatus was fixed in place; then the engineer, after having made his
companions go away, filled the hole so that the fluid overflowed the opening,
and spread some drops underneath the mass of suspended iron.</p>
<p>This done, Smith lit the end of the sulfured fibre, and, leaving the place,
returned with his companions to the Chimneys.</p>
<p>Twenty-five minutes after a tremendous explosion was heard. It seemed as if the
whole island trembled to its base. A volley of stones rose into the air as if
they had been vomited from a volcano. The concussion was such that it shook the
Chimneys. The colonists, though two miles away, were thrown to the ground.
Rising again, they clambered up to the plateau and hurried towards the place.</p>
<p>A large opening had been torn in the granite coping. A rapid stream of water
escaped through it, leaping and foaming across the plateau, and, reaching the
brink, fell a distance of 300 feet to the shore below.</p>
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