The mountain crept around to our left, as we flew on toward the mine. Suddenly Bill shouted and pointed toward the peak. I looked. Above the dark outline of the cone, a huge globe of blue light was rising, flaming with an intense brilliance that gave a ghastly tint of blue to all that desert wilderness of peaks! Like a great moon of blue fire, it rose swiftly into the sky! It dwindled, faded, was gone! I felt the hair rise on my neck. I was glad that our plane was swift and far away. If it was a human power with which we had to deal, I thought, it must have made strange advances. And then I remembered the strange noises upon the ether--sounds more like the stridulations of great insects than the voices of men! "That has happened twice before," Bill said. "But I didn't tell anybody about it in the States. It's too damned unbelievable." At the Thorium Mine In half an hour we were fifty miles south of Mocolynatal, circling over the mine. El Tigre Mine is near the center of a rocky, triangular plateau. Northwest and southwest, the Sierra Madre rises. On the east side of the triangle is the river, a tributary of the Nazas, in a canyon deep enough to hold the stream a hundred times. Perhaps a dozen square miles are so enclosed. It is a desert of sand and rocks, cut up with dry arroyos, scantily covered with yucca, mesquite, and cactus. The mine buildings stand on the little stream that cuts a track of vivid green across the neutral gray of the waste to the canyon below. Sitting there on the dull-hued plain, with the Cordillerras rising so abruptly a few miles back, the buildings looked very tiny and insignificant. Across the stream from the shaft-house, the shops, and the quarters of the men is a square, fortress-like two story residence of rough gray stone.... The narrow-gauge railroad track runs from it down toward the canyon like thin black threads. As we flew over the buildings, a trim white figure appeared on the roof of the residence, and waved a slender arm. I knew that it must be Ellen, and I felt oddly excited at the thought of seeing her again. Bill touched the button that released the rotor, and the machine settled lightly to earth near the main building. A short waddling person and a slender active one--the Doctor and Ellen--came out of the house and hurried toward us. "Why h-h-h-h-hello, Bob, I'm s-sur-surprised to see you," the Doctor rattled off. I have always had the opinion that he wouldn't stammer if he would take time to talk, but he is always in a hurry. "You're w-w-w-welcome, though. Looks like a new m-ma-ma-machine you have, Bill. The red ship c-c-c-came again while you were gone. I've got something to t-t-t-t-tell you. But get out and come in to the shade."