He threw open a door in the side of the metal cylinder. Blake stood back for only a moment to size up the machine, to observe its smooth duralumin shell and the rounded ends where portholes opened for the expelling of its driving blast. The door opening showed a thick wall that gave insulation. Blake followed the inventor to the interior of the ship. * * * * * The man had seen Winslow examining the thick walls. "It's cold out there, you know," he said, and smiled in recollection, "but the generator kept us warm." He pointed to a simple cylindrical casting aft of the ship's center part. It was massive, and braced to the framework of the ship to distribute a thrust that Blake knew must be tremendous. Heavy conduits took the blast that it produced and poured it from ports at bow and stern. There were other outlets, too, above and below and on the sides, and electric controls that were manipulated from a central board. "You've got a ship," Blake admitted, "and it's a beauty. I know construction, and you've got it here. But what is the power? How do you drive it? What throws it out through space?" "Aside from one other, you will be the only man ever to know." The bearded man was quiet now and earnest. The wild light had faded from his eyes, and he pondered gravely in making the last and final decision. "Yes, you shall have it. It may be I have been mistaken. I have known people--some few--who were kindly and decent; I have let the others prejudice me. But there was one who was my companion--and there was McGuire, who was kind and who believed. And now you, who will give your life for a friend and to save humanity!... You shall have it. You shall have the ship! But I will not go with you. I want nothing of glory or fame, and I am too old to fight. My remaining years I choose to spend out here." He pointed where a window of heavy glass showed the outer world and a grave on a sloping hill. * * * * * "But you shall have full instructions. And, for the present, you may know that it is a continuous explosion that drives the ship. I have learned to decompose water into its components and split them into subatomic form. They reunite to give something other than matter. It is a liquid--liquid energy, though the term is inaccurate--that separates out in two forms, and a fluid ounce of each is the product of thousands of tons of water. The potential energy is all there. A current releases it; the energy components reunite to give matter again--hydrogen and oxygen gas. Combustion adds to their volume through heat. "It is like firing a cannon in there,"--he pointed now to the massive generator--"a super-cannon of tremendous force and a cannon that fires continuously. The endless pressure of expansion gives the thrust that means a constant acceleration of motion out there where gravity is lost.