It was two o'clock in the morning when Manuel stood at the foot of the four-hundred-foot hole and signaled up that the air was good. Talbot lowered the tools to him, and the gas container, and lastly went down himself. As already stated, Talbot had explored the underground workings of the mine not eighteen months before. Picking out the main tunnel and keeping a close watch for rattlers with electric torches, the two men went cautiously ahead. In places earth had fallen and had to be cleared away, but the formation for the most part was a soft rock and shale. They went slowly, for fear of starting slides. At a spot taking an abrupt turn--and it was here that the newer tunnel had broken through into the older gallery of the Wiley claim--Manuel caught swiftly at Talbot's arm. "What is that?" To straining ears came the unmistakable throb of machinery. They snapped off their torches and crouched in Stygian darkness. Not a ray of light was to be seen. Talbot knew that in following the ore stratum, the Wiley gallery took several twists. Laboriously he and Manuel advanced with the gas tube. It was stiflingly close. He counted the turns, one, two, three. Now the roar of machinery was a steady reverberation that shook the tunnel. He whispered to Manuel: "Go back and wait for me at the mouth of the shaft. Only one of us must risk taking the gas tube any nearer the enemy. Here, take my watch. It is now two-forty-five. If I don't rejoin you by four o'clock touch off the explosive." Manuel started to protest. "Do as I say," commanded Talbot. "The fate of the world is at stake. Give me an hour; but no longer--remember!" Left alone in the clammy darkness Talbot wiped the sweat from his face. Grabbing one end of the rope sling in which the tube was fastened, he pulled it ahead. There was a certain amount of unavoidable noise; rock rattled, earth fell; but he reasoned shrewdly enough that the roar of the machinery would drown this. Beyond a crevice created by a cave-in he saw an intense light play weirdly. He squirmed through the crevice and pulled the tube after him. His mind reconstructed the mine ahead. He recollected that when the lead of this mine had petered out, the owners had begun to sink the shaft deeper into the earth before abandoning the mine. This meant that the foot of the shaft, with the addition of an encroaching twenty feet of the southern gallery, was deeper by some several yards than the floor of the tunnel in which he stood. Here was the logical place to set the gas tube, nose pointed ahead.