We had crossed the summit, and I had increased the speed to ten miles per hour in haste to reach the trees, in spite of Sam's fear that the operation of the motors at anything like full capacity would create a disturbance in the ether that our hidden enemies would pick up. Suddenly I saw a strange thing skimming along over the bright forest before us--in our direction! It looked like a bright silver globe, many feet in diameter! It floated a few hundred feet above the trees, drifting smoothly along like a bright metal balloon in a very swift wind. There was no visible propulsive mechanism. I shouted a warning to Sam through the speaking tube, to stand by his little gun. Xenora laid a light hand on my shoulder and said, in a tense voice: "It is the Sleepers of Mutron, the slaves of the Lord of Flame! They will fight to death--they know not fear!" As the silver sphere drifted swiftly and silently down upon us, as though borne by an invisible wind, twice I caught a glimpse of a slender ray of purple flame, that darted out of it and moved searchingly over the bare greensward below. And then a rich purple beam fell suddenly and intensely upon the Omnimobile! When that misty finger of purple light discovered us, I saw a strange vortex of pale green fire spring up about the globe and reach out in our direction. Suddenly I realized that this ship was of the same appearance as the weird thing that had destroyed our cottage! Small hope, I thought, if that force of atomic disintegration were to be released again! I heard the rapid crashing of the machine gun, as Sam began to fire, and presently bursts of smoke appeared about the gleaming sphere. But to hit a relatively small and rapidly moving target even a mile away is no mean feat of marksmanship. I drove rapidly for the purple wood, but with little hope of getting there before the terrible red disintegration had melted us away. Suddenly I heard the drone of some of Sam's new machinery going into action. He had mounted his switches and dials in the conning-tower, so he could control it from where he stood. Vivid blue electric flame quivered and flashed over the metal parts of the machine as his new weapons went into play! The floating globe of silver drifted nearer, and the misty vortex of green fire about us grew more intense. A strange red glow stole over the vegetation around us, and a solitary purple tree ahead burst into crimson flame. Then the sparkling fingers of purple fire reached out at us again from the sphere. I wondered vaguely why the strange force was not acting upon us. I did not know, until it was all over, that Sam's vacuum tubes had set up a repulsive screen in the ether, protecting us from the electronic vortex!