Even in daylight, with its ruts and mud-holes and ledges of outcropping stone, it was difficult to distinguish from the dreary waste of the moor interspersed with boulders and clumps of naked bushes.

But, as he says, "he steered his course by the feel of the wind," his hat rammed low on his brow, his head down, stopping now and again from mere weariness of mind rather than of body--as if not his strength but his resolution were being overtaxed by the strain of endeavour half suspected to be vain, and by the unrest of his feelings.
In one of these pauses borne in the wind faintly as if from very far away he heard a sound of knocking, just knocking on wood.

He noticed that the wind had lulled suddenly.
His heart started beating tumultuously because in himself he carried the impression of the desert solitudes he had been traversing for the last six hours--the oppressive sense of an uninhabited world.

When he raised his head a gleam of light, illusory as it often happens in dense darkness, swam before his eyes.

While he peered, the sound of feeble knocking was repeated--and suddenly he felt rather than saw the existence of a massive obstacle in his path.