d 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 a