After a thoughtful silence, Arcot continued, "And there is another thing it may make possible in the future--a thing that may be hard to accept as a commercial proposition. We have a practically inexhaustible source of energy now, but we have no sources of minerals that will last indefinitely. Copper is becoming more and more rare. Had it not been for the discoveries of the great copper fields of the Sahara and in Alaska, we wouldn't have any now. Platinum is exhausted, and even iron is becoming more and more valuable. We are facing a shortage of metals. Do you realize that within the next two centuries we will be unable to maintain this civilization unless we get new sources of certain basic raw materials? "But we have one other chance now. The solution is--there are nine planets in this solar system! Neptune and Uranus are each far vaster than Earth; they are utterly impossible for life as we know it, but a small colony might be established there to refine metals for the distant Earth. We might be able to build domed and sealed cities. But first we could try the nearer planets--Mars, Venus, or some satellites such as our Moon. I certainly hope that this machine will make it possible." For some time they sat in silence as they sped along, high above the green plains of Indiana. Chicago lay like some tremendous jewel far off on the horizon to the right and ahead. Five miles below them the huge bulk of the Transcontinental plane seemed a toy as it swung slowly across the fields--actually traveling over six hundred miles an hour. At last Morey spoke. "You're right, Arcot. We'll have to think of the interplanetary aspects of this some day. Oh, there's Chicago! We'd better start the vacuum gas protector. And the radar. We may soon see some action." The three men immediately forgot the somewhat distant danger of the metal shortage. There were a number of adjustments to be made, and these were quickly completed, while the machine forged evenly, steadily ahead. The generator was adjusted to maximum efficiency, and the various tubes were tested separately, for though they were all new, and each good for twenty-five thousand hours, it would be inconvenient, to say the least, if one failed while they were in action. Each tested perfect; and they knew from the smooth functioning of the various relays that governed the generator, as the loads on it varied, that it must be working perfectly, at something less than one-half maximum rating. Steadily they flew on, waiting tensely for the first sign of a glow from the tiny neon tube indicator on the panel before Morey.