The horseman rode slowly toward the west, stopping once or twice to examine the wide circle of the horizon with eyes that were trained to note every aspect of the wilderness. On his right the plains melted away in gentle swell after swell, until they met the horizon. Their brown surface was broken only by the spiked and thorny cactus and stray bits of chaparral. On his left was the wide bed of a river which flowed through the sand, breaking here and there into several streams, and then reuniting, only to scatter its volume a hundred yards further into three or four channels. A bird of prey flew on strong wing over the water, dipped and then rose again, but there was no other sign of life. Beyond, the country southward rolled away, gray and bare, sterile and desolate.