Before dawn, El Tigre looked like a military encampment. In the glare of great searchlights, men were digging trenches, leveling a landing field for the planes, and planting the battery. The Doctor had his ray machine ready for use. I was much surprised at the discipline and efficiency of the well-trained Mexican troops. With the rising of the sun, a sentry's hail proclaimed the appearance of a score of dark specks above the grim outline of Mocolynatal--a fleet of red planes, coming to the attack! In a moment the camp was alive. The gun crews got to their posts, airplane engines were started, infantry were lined up in the freshly dug trenches, with machine guns and rifles ready. I saw the gleaming tip of the Doctor's great tube projecting above the huge glass dome. In a few minutes the planes were taking the air, flying to meet the coming ships. I was with them, in the Camel-back. I had often dreamed of the thrills of war in the air, and I was eager enough for the encounter. But, as it turned out, I was to play no noble part. The red machines flew toward us with astonishing speed. In a few minutes they were upon us. Because of the greater speed of my ship, I was flying a little ahead of the formation of Mexican planes. That circumstance probably saved my life, as things turned out. I was firing a burst to warm up my gun when there was a puff of smoke from the foremost machine of the red ships. I watched the tiny black projectile that came toward us, saw it pass far below me and burst into a thick cloud of gleaming purple vapor that rolled and coiled like a strange creature of the air. And the wings of my machine no longer caught the air! The controls were useless. I was drifting up. The radiation of that shining cloud had negated the gravity of the machine! Half a dozen more of the strange bombs burst behind me, and I saw the other ships drifting up, even more rapidly than mine, for they had been nearer the clouds. I kept firing for a minute, but I believe I hit none of the red ships. Soon they had passed beneath, in the direction of the mine. Helpless, I drifted on into the sky! I had a clear view of the battle at the mine. As the red machines came within range, the railway gun and the camouflaged seventy-fives began firing. One of the red ships suddenly went down in flames, and then two more. Whether they were hit, or were victims of the Vernon Ray, I do not know. But in a few minutes the vicinity of the mine was dotted with the coiling hills of purple gas from the gravity-destroying bombs. I saw railway cars and engines, guns and tanks, and even the railroad rails and the mining machinery, torn from their places and plunging into the air. Suddenly the huge glass dome was shattered, and a great object shot up through it--Dr. Vernon's terrible instrument!