Even as the whistling roar of its passage was rolling down upon us, Melvar spoke. How I admire the courage and indomitable resourcefulness of the girl. When I was hopelessly lost in despair, feeling all the desolation of this region and the infinite remoteness of the world of men, her pure rich voice and the warm living touch of her hand brought new courage to me. "The Krimlu are coming," she cried. "There is no use to try to fight them, or to try to outrun them. But that ship must be empty. The walls are metal and strong. Perhaps they could not open it." While there were several things about the proposition that were not very attractive, it seemed our best resource; and, besides, I had a keen desire to see the interior of the thing. We gathered up our equipment, climbed off the boulder, and hurried over to the cylinder. I was possessed by a haunting fear that we would find something hideous awaiting us, but the bright pencil of light from my pocket lamp revealed no living being in the long interior, nor could I find even a trace of the green patch that had blown up in front of the door. We scrambled through the opening without difficulty and I turned a handle that swung the heavy door shut and evidently locked it. Then I set about examining the mechanism, for I had an intense curiosity about the propulsive force that enabled the vessel to attain a speed that must have reached thousands of miles per hour. In one end were rows of long cylinders of a transparent substance, evidently filled with the metallic fluid from the Silver Lake. Pipes ran from them to a complex mechanism in the rear end of the ship, from which heavy conduits ran all over the inside of the metal hull. While my understanding of it all was far from complete, I was able to verify a previous idea--that the strange vessels were driven by use of the rocket principle. It seems that the silver fluid was decomposed in the machine, and that the purple gas it formed, at a very high temperature, was forced out through the various tubes at a terrific velocity, propelling the ship by its reaction. The whistling roar of the things in motion was, of course, the sound of the escaping gas, and the red-purple tracks were merely the expelled gas hanging in the air. The green globe in the forward end may have been the objective lens for a marvelous periscope. At any rate the walls of the forward part of the shell seemed transparent. And the periscope must have utilized infra-red rays, for the scene about us seemed much brighter than it, in reality, was. We could see very plainly the burned plain and the granite rock, and once, through a rift in the clouds of smoke that were rising all about, I caught a glimpse of the gleaming city of Astran, high above us in the west.