Lonesome Dove, Volume 2: Comanche Moon by Larry McMurtry

BY MORNING Augustus McCrae was so tired that he had lost the ability to tell up from down. The dawn was sleet gray, the plain sleet gray as well. There was not a feature to stop the eye on the long plain: no tree, ridge, rise, hill, dip, animal, or bird. Augustus could see nothing at all, and he was well known to have the best vision in the troop. The plain was so wide it seemed you could see to the rim of forever, and yet, in all that distance, there was nothing. Augustus, like the other rangers, had been in the saddle thirty-six hours. Before the chase started he had been up all night, whoring and drinking; now he was so tired he thought he might be losing his mind. There were those among his comrades who thought that it was excessive whoring and drinking that had caused Gus's hair to turn white, almost overnight; but his own view was that too many long patrols had fatigued his hair so that it had lost its color.

Now, when he looked up, the horizon seemed to roll. It was as if the plain was turning over, like a plate. Augustus's stomach, which had little in it, began to turn, too. For a moment, he had the sensation that the sky was below him, the earth above. He needed to see something definite-an antelope, a tree, anything-to rid himself of the queasy sensation he got when the land seemed to tip. It grew so bad, the rolling, that at one point he felt his own horse was above him, its feet attached to the sky.