Moreover, the air had become so hot and stifling that she could scarcely breathe.
"It will be better presently," said Ithiel, noticing her distress, as he drew her limping after him into what seemed to be a natural crevice of rock hardly large enough to allow the passage of his body.

Along this crevice they scrambled for eight or ten paces, to find themselves suddenly in a tunnel lined with masonry, and so large that they could stand upright.
"Once it was a watercourse," explained Ithiel, "that filled the great tank, but now it has been dry for centuries." Down this darksome shaft hobbled Miriam, till presently it ended in a wall, or what seemed to be a wall--for when Ithiel pressed upon a stone it turned.

Beyond it the tunnel continued for twenty or thirty paces, leading them at length into a vast chamber with arched roof and cemented sides and bottom, which in some bygone age had been a water-tank.

Here lights were burning, and even a charcoal fire, at which a brother was engaged in cooking.

Also the air was pure and sweet, doubtless because of the winding water-channels that ran upwards.