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 them. But-- "Well?" said Bordman challengingly. "This is the site of the landing-grid," said Redfeather. "Where?" "Here," said the Indian. "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." It was hot. Horribly, terribly hot, even here on a plateau at mountain top 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 needs. 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--?"