By an open window, where a hot breeze stirred sluggishly, Rawson sat in silent contemplation of the camp. His face was as copper-colored as an Apache's and as motionless. His eyes were fixed unwaveringly upon a distant derrick and the blasted stub of a big drill that hung unmoving above the concrete floor. But the man's eyes did not consciously record the details of that scene. He saw nothing of the derrick or of the heat waves that made the steel seem writhingly alive; he was looking at something far more distant, something many miles away, something vague and mysterious, hidden miles beneath the surface of the earth. "Heat," he said at last, as if talking in a dream. "Heat, terrific temperatures--but I can't make it out; I can't see it!" The younger, broad-shouldered man, whose khaki shirt, thrown open at the neck showed a chest tanned to the black-brown of his face, stopped his restless pacing back and forth in the hot room. "Yes?" he asked with a touch of irritation in his tone. "There's plenty of heat there--heat enough to melt off the shaft of that high-temp alloy! What the devil's the use of wondering about the heat, Dean? What gets me is this: the shaft has been plugged again. Now, what kind of...." * * * * * Dean Rawson's face had not moved a muscle during the other's outburst. His eyes were still fixed on that place that was so far away, yet which he tried to bring close in his mind, close enough to see, to comprehend the mystery that should be so plain. "Lava wouldn't do it!" he said softly. "No melted stone would melt the Krieger alloy, unless it was under pressure, which this was not. There was no blast coming out of our shaft. Yet we dipped into that gold; we stuck the drill right down into it. But what did we go into the next time? What did we dip into?" He swung quickly, violently, toward Smithy who was facing him from the middle of the room. He aimed one finger at him as if it were a pistol, and his words cracked out as sharply as if they came from a gun: "That tube you sent down--that piece of casing! How was it burned? Were there straggling ends, frozen gobs of metal? Did it look like an old-fashioned molasses candy bar that's been melted? Did it?" "Why, no," said Smithy. "It hadn't dripped any; it was cut off nice and clean." "Cut!" Rawson almost shouted the word. "You said it, Smithy. So was the shaft of the drill. And if you ever saw a piece of this alloy being melted you know that it's as gummy as a pot of old paint. It was cut, Smithy! Dipping into that melted gold threw us off the track; we were thinking of ramming the drill down into a mess of lava. But we didn't. It was cut off by a blast of flame so much hotter than lava that melted rock would seem cold!" "And that helps us a lot, doesn't it," asked Smithy, scornfully, "when the flame melts the end of the shaft shut as fast as we open it?"