The next day, the 5th of June, in rather uncertain weather, they set out for the islet.
They had to profit by the low tide to cross the Channel, and it was agreed that they would construct, for this purpose, as well as they could, a boat which would render communication so much easier, and would also permit them to ascend the Mercy, at the time of their grand exploration of the southwest of the island, which was put off till the first fine days.
The seals were numerous, and the hunters, armed with their iron-tipped spears, easily killed half-a-dozen.

Neb and Pencroft skinned them, and only brought back to Granite House their fat and skin, this skin being intended for the manufacture of boots.
The result of the hunt was this: nearly three hundred pounds of fat, all to be employed in the fabrication of candles.
The operation was extremely simple, and if it did not yield absolutely perfect results, they were at least very useful.

Cyrus Harding would only have had at his disposal sulphuric acid, but by heating this acid with the neutral fatty bodies he could separate the glycerine; then from this new combination, he easily separated the olein, the margarin, and the stearin, by employing boiling water.

But to simplify the operation, he preferred to saponify the fat by means of lime.

By this he obtained a calcareous soap, easy to decompose by sulphuric acid, which precipitated the lime into the state of sulphate, and liberated the fatty acids.
From these three acids-oleic, margaric, and stearic-the first, being liquid, was driven out by a sufficient pressure.