They began to experience the cravings of thirst.

The butte still appeared at a great distance--at least ten miles off.

What, if on reaching it, they should find no water?
This thought, combined with the torture they were already enduring, was enough to fill them with apprehension and fear.
Basil now felt how inconsiderately they had acted, in not listening to the more prudent suggestions of Lucien; but it was too late for regrets--as is often the case with those who act rashly.
They saw that they must reach the butte as speedily as possible, for the night was coming on.

If it should prove a dark night, they would be unable to guide themselves by the eminence, and losing their course might wander all night.

Oppressed with this fear, they pushed forward as fast as possible; but their animals, wearied with the long journey and suffering from thirst, could only travel at a lagging pace.
They had ridden about three miles from the dog-town, when, to their consternation, a new object presented itself.