Pencroft had expressly declared this.

Now, to construct a simple boat even with the necessary tools, was a difficult work, and the colonists not having tools they must begin by making hammers, axes, adzes, saws, augers, planes, etc., which would take some time.

It was decided, therefore, that they would winter at Lincoln Island, and that they would look for a more comfortable dwelling than the Chimneys, in which to pass the winter months.
Before anything else could be done it was necessary to make the iron ore, of which the engineer had observed some traces in the northwest part of the island, fit for use by converting it either into iron or into steel.
Metals are not generally found in the ground in a pure state.

For the most part they are combined with oxygen or sulphur.

Such was the case with the two specimens which Cyrus Harding had brought back, one of magnetic iron, not carbonated, the other a pyrite, also called sulphuret of iron.