第56章

Neb and Pencroft were first of all told to extract the grease from the dugong, and to keep the flesh, which was destined 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 shistose 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 shistose 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 shistose 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 shist, 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, and it would not take less than ten or twelve days for the sulphuret of iron to be changed to 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, while 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 fucaceae 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, nitrate of potash, which is better known under the name of salt niter, or of saltpeter.

Cyrus Harding 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 saltpeter, 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 or iron when it had been obtained.All this was finished about the 18th 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 basinful 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.