"Only about a hundred feet, and we do not seem to be getting any deeper."

"That's good. Afraid this beam might be going to a station on the other side of the planet--through the ground. If so, we'd have had to go back and trace another. We can follow it any distance under water, but not through rock. Need a light?"

"Not unless we go deeper."

For two hours Seaton held the detector upon that tight beam of energy, traveling at a hundred miles an hour, the highest speed he could use and still hold the beam.

"I'd like to be up above watching us. I bet we're making the water boil behind us," remarked Dorothy.

"Yeah, we're kicking up quite a wake, I guess. It sure takes power to drive the old can through this wetness."

"Slow down!" commanded Crane. "I see a submarine ahead. I thought it might be a whale at first, but it is a boat and it is what we are aiming for. You are constantly swinging with it, keeping it exactly in the line."

"O.K." Seaton reduced the power and swung the visiplate over in front of him, whereupon the detector lamp went out. "It's a relief to follow something I can see, instead of trying to guess which way that beam's going to wiggle next. Lead on, Macduff--I'm right on your tail!"

The _Skylark_ fell in behind the submersible craft, close enough to keep it plainly visible in the telescopic visiplate. Finally the stranger stopped and rose to the surface between two rows of submerged pontoons which, row upon row, extended in every direction as far as the telescope could reach.

"Well, Dot, we're where we're going, wherever that is."

"What do you suppose it is? It looks like a floating isleport, like what it told about in that wild-story magazine you read so much."

"Maybe--but if so they can't be fish," answered Seaton. "Let's go--I want to look it over," and water flew in all directions as the _Skylark_ burst out of the ocean and leaped into the air far above what was in truth a floating city.

Rectangular in shape, it appeared to be about six miles long and four wide. It was roofed with solar generators like those covering the island just visited, but the machines were not s.p.a.ced quite so closely together, and there were numerous open lagoons. The water around the entire city was covered with wave-motors. From their great height the visitors could see an occasional submarine moving slowly under the city, and frequently small surface craft dashed across the lagoons. As they watched, a seaplane with short, thick wings curved like those of a gull, rose from one of the lagoons and shot away over the water.

"Quite a place," remarked Seaton as he swung a visiplate upon one of the lagoons. "Submarines, speedboats, and fast seaplanes. Fish or not, they're not so slow. I'm going to grab off one of those folks and see how much they know. Wonder if they're peaceable or warlike?"

"They look peaceable, but you know the proverb," Crane cautioned his impetuous friend.

"Yes, and I'm going to be timid like a mice," Seaton returned as the _Skylark_ dropped rapidly toward a lagoon near the edge of the island.

"You ought to put that in a gag book, d.i.c.k," Dorothy chuckled. "You forget all about being timid until an hour afterwards."

"Watch me, Red-top! If they even point a finger at us, I'm going to run a million miles a minute."

No hostile demonstration was made as they dropped lower and lower, however, and Seaton, with one hand upon the switch actuating the zone of force, slowly lowered the vessel down past the reflectors and to the surface of the water. Through the visiplate he saw the crowd of people coming toward them--some swimming in the lagoon, some walking along narrow runways. They seemed to be of all sizes, and unarmed.

"I believe they're perfectly peaceable, and just curious, Mart. I've already got the repellers on close range--believe I'll cut them off altogether."

"How about the ray-screens?"

"All three full out. They don't interfere with anything solid, though, and won't hurt anything. They'll stop any ray attack and this arenak hull will stop anything else we are apt to get there. Watch this board, will you, and I'll see if I can't negotiate with them."

Seaton opened the door. As he did so, a number of the smaller beings dived headlong into the water, and a submarine rose quietly to the surface less than fifty feet away with a peculiar tubular weapon and a huge ray-generator trained upon the _Skylark_. Seaton stood motionless, his right hand raised in the universal sign of peace, his left holding at his hip an automatic pistol charged with X-plosive sh.e.l.ls--while Crane, at the controls, had the Fenachrone super-generator in line, and his hand lay upon the switch, whose closing would volatilize the submarine and cut an incandescent path of destruction through the city lengthwise.

After a moment of inaction, a hatch opened, a man stepped out upon the deck of the submarine, and the two tried to converse, but with no success. Seaton then brought out the mechanical educator, held it up for the other's inspection, and waved an invitation to come aboard.

Instantly the other dived, and came to the surface immediately below Seaton, who a.s.sisted him into the _Skylark_. Tall and heavy as Seaton was, the stranger was half a head taller and almost twice as heavy. His thick skin was of the characteristic Osnomian green and his eyes were the usual black, but he had no hair whatever. His shoulders, though broad and enormously strong, were very sloping, and his powerful arms were little more than half as long as would have been expected had they belonged to a human being of his size. The hands and feet were very large and very broad, and the fingers and toes were heavily webbed. His high domed forehead appeared even higher because of the total lack of hair, otherwise his features were regular and well-proportioned. He carried himself easily and gracefully, and yet with the dignity of one accustomed to command as he stepped into the control room and saluted gravely the three other Earth-beings. He glanced quickly around the room, and showed unmistakable pleasure as he saw the power-plant of the cruiser of s.p.a.ce. Languages were soon exchanged and the stranger spoke, in a ba.s.s voice vastly deeper than Seaton's own.

"In the name of our city and planet--I may say in the name of our solar system, for you are very evidently from one other than our green system--I greet you. I would offer you refreshment, as is our custom, but I fear that your chemistry is but ill adapted to our customary fare.

If there be aught in which we can be of a.s.sistance to you, our resources are at your disposal--but before you leave us, I shall wish to ask from you a great gift."

"Sir, we thank you. We are in search of knowledge concerning forces which we cannot as yet control. From the power systems you employ, and from what I have learned of the composition of your suns and planets, I a.s.sume you have none of the metal of power, and it is a quant.i.ty of that element that is your greatest need?"

"Yes. Power is our only lack. We generate all we can with the materials and knowledge at our disposal, but we never have enough. Our development is hindered, our birth-rate must be held down to a minimum, many new cities which we need cannot be built and many new projects cannot be started, all for lack of power. For one gram of that metal I see plated upon that copper cylinder, of whose very existence no scientist upon Dasor has had even an inkling, we would do almost anything. In fact, if all else failed, I would be tempted to attack you, did I not know that our utmost power could not penetrate even your outer screen, and that you could volatilize the entire planet if you so desired."

"Great Cat!" In his surprise Seaton lapsed from the formal language he had been employing. "Have you figured us all out already, from a standing start?"

"We know electricity, chemistry, physics, and mathematics fairly well.

You see, our race is many millions of years older than is yours."

"You're the man I've been looking for, I guess," said Seaton. "We have enough of this metal with us so that we can spare you some as well as not. But before you get it, I'll introduce you. Folks, this is Sacner Carfon, Chief of the Council of the planet Dasor. They saw us all the time, and when we headed for this, the Sixth City, he came over from the capital, or First City, in the flagship of his police fleet, to welcome us or to fight us, as we pleased. Carfon, this is Martin Crane--or say, better than introductions, put on the headsets, everybody, and get acquainted right."

Acquaintance made and the apparatus put away, Seaton went to one of the store-rooms and brought out a lump of "X," weighing about a hundred pounds.

"There's enough to build power-plants from now on. It would save time if you were to dismiss your submarine. With you to pilot us, we can take you back to the First City a lot faster than your vessel can travel."

Carfon took a miniature transmitter from a pouch under his arm and spoke briefly, then gave Seaton the course. In a few minutes, the First City was reached, and the _Skylark_ descended rapidly to the surface of a lagoon at one end of the city. Short as had been the time consumed by their journey from the Sixth City, they found a curious and excited crowd awaiting them. The central portion of the lagoon was almost covered by the small surface craft, while the sides, separated from the sidewalks by the curbs, were full of swimmers. The peculiar Dasorian equivalents of whistles, bells, and gongs were making a deafening uproar, and the crowd was yelling and cheering in much the same fashion as do earthly crowds upon similar occasions. Seaton stopped the _Skylark_ and took his wife by the shoulder, swinging her around in front of the visiplate.

"Look at that, Dot. Talk about rapid transit! They could give the New York subway a flying start and beat them hands down!"

Dorothy looked into the visiplate and gasped. Six metal pipes, one above the other, ran above and parallel to each sidewalk-lane of water. The pipes were full of ocean water, water racing along at fully fifty miles an hour and discharging, each stream a small waterfall, into the lagoon.

Each pipe was lighted in the interior, and each was full of people, heads almost touching feet, unconcernedly being borne along, completely immersed in that mad current. As the pa.s.senger saw daylight and felt the stream begin to drop, he righted himself, apparently selecting an objective point, and rode the current down into the ocean. A few quick strokes, and he was either at the surface or upon one of the flights of stairs leading up to the platform. Many of the travelers did not even move as they left the orifice. If they happened to be on their backs, they entered the ocean backward and did not bother about righting themselves or about selecting a destination until they were many feet below the surface.

"Good heavens, d.i.c.k! They'll kill themselves or drown!"

"Not these birds. Notice their skins? They've got a hide like a walrus, and a terrific layer of subcutaneous fat. Even their heads are protected that way--you could hardly hit one of them enough with a baseball bat to hurt him. And as for drowning--they can out-swim a fish, and can stay under water almost an hour without coming up for air. Even one of those youngsters can swim the full length of the city without taking a breath."

"How do you get that velocity of flow, Carfon?" asked Crane.

"By means of pumps. These channels run all over the city, and the amount of water running in each tube and the number of tubes in use are regulated automatically by the amount of traffic. When any section of tube is empty of people, no water flows through it. This was necessary in order to save power. At each intersection there are four stand pipes and automatic swim-counters that regulate the volume of water and the number of tubes in use. This is ordinarily a quiet pool, as it is in a residence section, and this channel--our channels correspond to your streets, you know--has only six tubes each way. If you will look on the other side of the channel, you will see the intake end of the tubes going down-town."

Seaton swung the visiplate around and they saw six rapidly-moving stairways, each crowded with people, leading from the ocean level up to the top of a tall metal tower. As the pa.s.sengers reached the top of the flight they were catapulted head-first into the chamber leading to the tube below.

"Well, that is some system for handling people!" exclaimed Seaton.

"What's the capacity of the system?"

"When running full pressure, six tubes will handle five thousand people a minute. It is only very rarely, on such occasions as this, that they are ever loaded to capacity. Some of the channels in the middle of the city have as many as twenty tubes, so that it is always possible to go from one end of the city to the other in less than ten minutes."

"Don't they ever jam?" asked Dorothy curiously. "I've been lost more than once in the New York subway, and been in some perfectly frightful jams, too--and they weren't moving ten thousand people a minute either."

"No jams ever have occurred. The tubes are perfectly smooth and well-lighted, and all turns and intersections are rounded. The controlling machines allow only so many persons to enter any tube--if more should try to enter than can be carried comfortably, the surplus pa.s.sengers are slid off down a chute to the swim-ways, or sidewalks, and may either wait a while or swim to the next intersection."

"That looks like quite a jam down there now." Seaton pointed to the receiving pool, which was now one solid ma.s.s except for the s.p.a.ce kept clear by the six mighty streams of humanity-laden water.

"If the newcomers can't find room to come to the surface they'll swim over to some other pool." Carfon shrugged indifferently. "My residence is the fifth cubicle on the right side of this channel. Our custom demands that you accept the hospitality of my home, if only for a moment and only for a beaker of distilled water. Any ordinary visitor could be received in my office, but you must enter my home."