The yellow flaring of their lights through the intense darkness proved both guidance and warning, so he moved cautiously forward, counting his steps, his hand feeling the trend of the side wall, his lamp unlit.

The floor was rough and uneven, but dry, the tunnel apparently having been blasted through solid rock, for no props supporting the roof were discernible.

For quite an extended distance this entry ran straight away from the foot of the shaft--directly south he made it--into the heart of the mountain; then those twinkling lights far in advance suddenly winked out, and Winston groped blindly forward until he discovered a sharp turn in the tunnel.
He lingered for a moment behind the protection of that angle of rock wall, struck a safety match, and held the tiny flame down close against the face of his pocket compass.

Exactly; this new advance extended southeast by east.

He snuffed out the glowing splinter between his fingers, crossed over to the opposite side, and watchfully rounded the corner to where he could again perceive the twinkling lights ahead.
His foot met some obstacle along the floor, and he bent down, feeling for it with his fingers in the dark; it proved to be a rude scrap-iron rail, evidence that they carried out their ore by means of mules and a tram-car.