 What was Rolf looking for when he set off around the wall of the pit?
"They may have found the sunken seas of Mars," thought Rolf as he moved alertly forward, "water that would give the mining domes new life." As the spinner dropped him slowly down into the vast emptiness of the great shining gulf, Rolf could see that a broad band of stone divided the green fertile plains and forests from the desolate desert wastes of the other half. Toward this barrier the spinner bore him, and Rolf was content to let it move in that direction—from the heights of the wall he could scout out the country beyond. Deftly Rolf nested the spinners again in their pack before he set out toward the heaped-up mass of stone blocks that was the wall.
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