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, they found Herbert and Pencroft 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 penetrate 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, 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.