After a while Adam discovered that when he trudged down into the hollows between dunes he became enveloped in flying sand that forced him to cover mouth and eyes with his scarf and go choking on, but when he climbed up over a dune the air became clearer and he could breath easier. Thus instinctively he favored the ascents, and thus he lost himself in a world of curved and sculptured sand dunes, gray and yellow through the flying mists, or steely silver under the gleaming sunlight. The wind lulled, letting the sand settle, and then he saw he was lost as upon a trackless ocean, with no landmarks in sight. On all sides heaved beautiful white mounds of sand, ribbed and waved and laced with exquisitely delicate knife-edged curves. And these crests changed like the crests of waves, only, instead of flying spray, these were curled and shadowed veils of sand blowing from the scalloped crowns. Then again the wind, swooping down, whipped and swept the sand in low thick sheets on and on over the dunes, until thin rising clouds obscured the sky. Adam climbed on, growing weaker. As the heat had wrought strangely upon his blood, so the sand had dragged strength from his legs. His situation was grave, but, though he felt the dread and pity of it, a certain violence of opposition had left him. That was in his will. He feared more the instinctive reaction--the physical resistance that was growing in him. Merryvale had told him how men lost on the desert could die of thirst in one day. But Adam had scarcely credited that; certainly he did not believe it applicable to himself. He realized, however, that unless he somehow changed the present condition sun and sand would overwhelm him. So when from a high knoll of sand he saw down into a large depression, miles across, where clumps of mesquites showed black against the silver, he descended toward them and eventually reached them, ready indeed to drop into the shade. Here under a thick-foliaged mesquite he covered his face with a handkerchief, his head with his coat, and settled himself to rest and wait. It was a wise move. At once he felt by contrast what the fierce sun had been. Gradually the splitting headache subsided to a sensation that seemed to Adam like a gentle boiling of blood in his brain. He could hear it. His dry skin became a little moist; the intolerable burn left it; his heart and pulse ceased such labored throbbing; and after a time his condition was limited to less pain, a difficulty in breathing, and thirst. These were bearable. From time to time Adam removed the coverings to look about him. The sun was westering. When it sank the wind would cease to blow and then he could find a way out of this wilderness of sand dunes. Leaning back against a low branch of the tree, he stretched out, and such was his exhaustion and the restfulness of the posture that he fell asleep.