"No," he answered; "everything depends on the nature of the material. If it is a pure ore of uranium, there will be no explosion but only a radioactive discharge from the surface, which will drive the asteroid out of its present path. If there are other materials present, things will fly. Medusa is about one hundred and fifty miles in diameter. It is scarcely conceivable that our ray could actually break it up. But I'm not going to take any chances. Medusa may be within range now. I think we had better try her at this distance." Through their glasses, they could easily see that on one side the surface of the asteroid was pitted with holes and craters similar to those upon the moon, while the other, which had been subjected to the fierce erosion of the dense gases of the comet, was worn almost smooth and plowed into furrows. The Ring was now moving on a course parallel to that of Medusa, which floated apparently motionless in space at a distance which Bennie estimated to be less than five hundred miles. Both, drawn by the combined attraction of the sun and earth, were in reality rushing on toward the latter. The three men were busy with their preparations for the projection of the great ray, and Rhoda drew herself over to the side deadlight, through which streamed the pale-yellow beams from the runaway planet. Now that they were running alongside, but one-half of the illuminated hemisphere was visible, and Medusa appeared like the moon at the half-phase, but fifty times as big. Monstrous and sinister it looked to her, and she shuddered involuntarily as she thought of its distant target, peopled with millions of helpless human beings, doomed to be wiped out of existence in a blinding flash of fire. Could they do aught to prevent it--four insects in a flying pellet of metal, aspiring to stop a runaway world? Had not perhaps the thing been put in motion by some Supreme Intelligence which controlled the universe, and might not the destruction of the world be a part of the Great Plan, a cog in the great wheel of destiny? If so, what could they hope to do to alter the plan? And then she thought of the taming of the thunderbolt by the lightning-rod, and drew a long breath and clenched her hands. Man had, from the beginning, devised ways and means of averting impending disasters due to the forces of nature. The present case differed in no respect from the others except in magnitude. The evolution of defense against nature had been steady and progressive, from the stone age, when prehistoric man sought shelter in caves from the pelting hailstones, to the present one in which they were about to whip out of its course a planet that was running wild through the solar system.