tug headed straight across the current for the landing at Beni Yeb. A triangular gleam marked the roof of a house which threw out its flat, cemented angle from a clump of palms, flanked by denser vegetation. The vivid greens contrasted brilliantly after so many miles of dirty yellow.
Lyttleton pointed. "Look, Colonel, and see what irrigation may accomplish."
At this moment Colonel Spottiswoode was not thinking of irrigation. His eyes and mind were fascinated by a shimmering mirage which he had been watching for an hour.
"That water is perfectly plain," he remarked, "and those palm trees as distinct as trees on this side of the river."
"So they are," assented Lyttleton, "yet there's nothing but desert."
"And you say it's all imagination; or rather an optical illusion?" the Colonel asked incredulously. "For instance, you and I may count those palm trees and agree as to the number; both of us see precisely the same thing—which cannot be imagination."
The Colonel counted: "One, two, three—I see seven palms: four in a cluster, two others close together, and one stands off a little farther to the left."
Lyttleton nodded, "Quite true; that's what I see."
