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.