At a touch upon a lever the propeller that Dick was watching, and which was rotating very slowly, suddenly gathered speed, till it was but a mere haze in the distance. He felt the whole ship move forward, while a touch on another lever bent the propeller downward, and to his consternation the deck he stood on canted badly, the vessel headed downward and went hurtling towards that muddy ocean which he could see below him. The sensation was in fact paralysing. It was worse, perhaps, when it was reversed, and the nose of the ship shot upward, setting the deck at such an angle that Dick had to cling hard to the railings fending the motors. But a moment later, at a touch from the inventor, she came to an even keel, the propeller ceased to rotate, while the vessel came to a halt. "Now, see how we rise at will," said Joe, watching Dick's face with delight, for it pleased the young inventor to notice the open admiration with which the youthful sailor regarded everything. "Now, I pull this handle. We fall. I reverse the movement. We shoot upward, but always keeping the horizontal position." It was really remarkable, for the mere touch of the inventor sent the ship up and down, for all the world as if she were suspended in space, and his fingers controlled the switch of some hoisting machinery. "How's it done?" asked Dick eagerly. "How does the power get to that propeller, for instance? Your motors are here. There are no chains, no shafts, nothing save these cased-in things at the end of each motor, which might be pumps for all I know." "And happen to be exactly what you have mentioned. They are pumps, of the rotary variety, and the material they deal with is that same common, crude paraffin on which our motors run. See those pipes. They are of the best, cold-drawn steel. They convey the oil from our pumps to the various propellers, to the lift and to any part where we have need for power. No corner is too sharp for them. They run anywhere, and, as you can imagine, convey the power of these engines with a certainty there is no gainsaying. Of course, at the far end we have other rotary motors. The oil pumped at this point, and under high pressure, is unable to escape from the steel pipes. At will we pass it into our distant motors, allowing some to escape back in this direction through a bypass. If the bypass is pulled wide open, the motors beyond do not turn; for the oil fails to reach them. If it is closed, there is no escape for the oil. It reaches the motors at its highest pressure, and operates them at full power, as powerfully, in fact, as if this engine down here driving the pumps was away up there close to the propeller with the shaft directly coupled to it. In short, and as an interesting fact, our propellers and other gear are operated by hydraulic power, applied after the latest principle."