THE HERITAGE OF THE SIOUX
the lost horses, until the vision changed and shrunk the moving objects to mere dots upon the mesa.
Often before they had watched the fantastic air-pictures of the desert mirage, and they knew well enough that what they saw might be one mile away or twenty. But unless the atmospheric conditions happened to be just right, what was pictured in the air could not be depended upon to portray truthfully what was reflected. They sat there and saw the animals suddenly grow clearly defined and very close, and discovered at last that they were sheep, and that a man was walking beside the flock; and even while they watched it and wondered if the sheep were really as close as they seemed, the vision slowly faded into blank, wavery distance and the mesa lay empty and quivering under the sun.
"Fine chance we've got of locating anything," Andy grumbled, "if it's going to be miragy all day. We could run our fool heads off trying to get up to a bunch that would puff out into nothing. Makes a fellow think of the stories they tell about old prospectors going crazy trying to find mirage water-holes. I'm glad we didn't get hung up at
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