The journey went on for an hour. Then there came a straining climb up a now-windswept ridge of eroded rock, and the attainment of its highest point. The ground car went onward for a hundred yards and stopped. They had reached the top of the mountain range, and there was doubtlessly another range beyond. But they could not see it. Here, at the place to which they had climbed so effortfully, there were no more rocks. There was no valley. There was no descending slope. There was sand. This was one of the sand plateaus which were a unique feature of Xosa II. And Bordman knew, now, that the disputed explanation was the true one. Winds, blowing over the mountains, carried sand as on other worlds they carried moisture and pollen and seeds and rain. Where two mountain ranges ran across the course of long-blowing winds, the winds eddied above the valley between. They dropped sand into it. The equivalent of trade winds, Bordman considered, in time would fill a valley to the mountain tops, just as trade winds provide moisture in equal quantity on other worlds, and civilizations have been built upon it. But---- * * * * * "Well?" said Bordman challengingly. "This is the site of the landing grid," said Redfeather. "Where?" "Here," said the Indian dryly. "A few months ago there was a valley here. The landing grid had eighteen hundred feet of height built. There was to be four hundred feet more--the lighter top construction justifies my figure of eighty per cent completion. Then there was a storm." [Illustration] It was hot. Horribly, terribly hot, even here on a plateau at mountaintop height. Dr. Chuka looked at Bordman's face and bent down in the vehicle. He turned a stopcock on one of the air tanks brought for Bordman's necessity. Immediately Bordman felt cooler. His skin was dry, of course. The circulated air dried sweat as fast as it appeared. But he had the dazed, feverish feeling of a man in an artificial-fever box. He'd been fighting it for some time. Now the coolness of the expanded air was almost deliriously refreshing. Dr. Chuka produced a canteen. Bordman drank thirstily. The water was slightly salted to replace salt lost in sweat. "A storm, eh?" asked Bordman, after a time of contemplation of his inner sensations as well as the scene of disaster before him. There'd be some hundreds of millions of tons of sand in even a section of this plateau. It was unthinkable that it could be removed except by a long-time sweep of changed trade winds along the length of the valley. "But what has a storm to do----"