Fully fifteen miles in diameter, it was a huge doughnut, a great ring of tubing with a center-opening that was at least eighty per cent of its maximum diameter. There it hovered, sending out those deadly missiles in a continuous stream toward our poor world. As we approached the weird space flier, we saw that a number of objects floated about within the great circle of its inner circumference. The NY-18, the SF-61 and the SF-22, without doubt! The theory of Hart's was correct in every detail. * * * * * We were still at about ten miles distance from the great ring and the streaking light pencils were speeding earthward at the rate of one a minute now. There was no time to lose. Already there was more destruction on its way than had been previously wrought--several times over. Hart was sighting along a tiny tube that projected into the forward partition and he maneuvered the _Pioneer_ until she was nose on to the great ring. He pulled a switch and there came a purring that was entirely new. A row of huge vacuum tubes along the wall lighted to vivid brilliancy and a throbbing vibration filled the artificial air of the cabin. He pulled a small lever at the side of the tube and the vessel rocked to the energy that was released from those vacuum tubes. The thin rod which had been installed at the _Pioneer's_ nose burst into brilliant flame--orange tinted luminescence that grew to a sphere of probably ten feet in diameter. Then there was a heavy shock and the ball of fire left its position and, with inconceivable velocity, sprang straight for the side of the great ring. It was a fair hit and, when the weird missile found its mark, it simply vanished--swallowed up in the metal walls of the monster vessel. For a moment we thought nothing was to result. Then we burst into shouts of joy, for a great section of the ring fused into nothingness and was gone! Fully a quarter of the circumference of the ring had disappeared into the vacuum of space. Truly, the governments of Earth had developed some terrible weapons of their own! We watched, breathless. * * * * * The green light pencils no longer streaked their paths of death in the direction of our world, which now seemed so remote. The great ring with the vacant space in its rim wabbled uncertainly for a moment as though some terrific upheaval from within was tearing it asunder. Then it lurched directly for the _Pioneer_. We had been observed!