compliment you on the way you've handled yourselves these past few months. You boys are real spacemen!" He saluted and disappeared down the ladder leading to the exit port.

"And that," said Roger, turning to his unit-mates, "is known as the royal come-on for a dirty detail!"

"Ahhh, stop your gassing, Manning," growled Astro. "Just be sure your radar bridge is O.K. If we do have to blast out of here in a hurry, I want to get where we're supposed to be going!"

"You just worry about the power deck, spaceboy, and let little Roger take care of his own department," replied Roger.

Astro eyed him speculatively. "You know the only reason they allowed this space creep in the Academy, Tom?" asked Astro.

"No, why?" asked Tom, playing along with the game.

"Because they knew any time the Polaris ran out of reactant fuel we could just stick Manning in the rocket tubes and have him blow out some of his special brand of space gas!"

"Listen, you Venusian throwback! One more word out of you and—"

"All right, you two!" broke in Tom good-naturedly. "Enough's enough! Come on. We've got just enough time to run up to the mess hall and grab a good meal before we check the ship."

"That's for me," said Astro. "I've been eating those concentrates so long my stomach thinks I've turned into a test tube."

Astro referred to the food taken along on space missions. It was dehydrated and packed in plastic containers to save weight and space. The concentrates never made a satisfactory meal, even though they supplied everything necessary for a healthful diet.

A few moments later the three members of the Polaris stood on the main slidewalk, an endless belt of plastic, powered by giant subsurface rollers, being carried from the spaceport to the main academy administration building, the great gleaming Tower of Galileo.

Space Academy, the university of the planets, was set among the low hills of the western part of the North American continent. Here, in the nest of fledgling spacemen, boys from Earth and the colonies of Venus and Mars learned the complex science that would enable them to reach unlimited heights; to rocket through the endless void of space and visit new worlds on distant planets millions of miles from Earth.

This was the year 2353—the age of space! A time when boys dreamed only of becoming Space Cadets at Space Academy, to learn their trade and later enter the mighty Solar Guard, or join the rapidly expanding merchant space service that sent out great fleets of rocket ships daily to every corner of the solar system.

As the slidewalk carried the three cadets between the buildings that surrounded the grassy quadrangle of the Academy, Tom looked up at the Tower of Galileo dominating the entire area.

"You know," he began haltingly, "every time I go near this place I get a lump in my throat!"

"Yeah," breathed Astro, "me too."

Roger made no comment. His eyes were following the path of the giant telescope reflector that moved in a slow arc, getting into position for the coming night's observations. Tom followed his gaze to the massive domed building, housing the giant one-thousand-inch reflector.

"You think we'll ever go as far into the deep with a rocket ship as we can see with the big eye?" he asked.

"I dunno," replied Roger. "That thing can penetrate other star systems in our galaxy. And that's a long way off!"

"Nearest thing to us is Alpha Centauri in our own galaxy, and that's twenty-three and a half million million miles away," commented Astro.

"That's not so far," argued Tom. "Only a few months ago the Solar Alliance sent out a scientific exploration to take a look at that baby."

"Musta been some hop," commented Roger.

"Hey!" cried Tom suddenly. "There's Alfie Higgins!" He pointed in the direction of another slidewalk moving at right angles to their own. The cadet that he singled out on the slidewalk was so thin and small he looked emaciated. He wore glasses and at the moment was absorbed in a paper he held in his hand.

"Well, what do you know!" cried Astro. "The Brain!"

Roger punched Astro in the mid-section. "If you were as smart as he is, you big grease monkey, you'd be O.K."

"Nah!" replied Astro. "If I was as smart as Alfie, I'd be scared. And besides, what do I need to be smart for? I've got you, haven't I?"

When they drew near the other slidewalk, the three members of the Polaris unit skipped lightly over and jostled their way past other riders to the slightly built cadet.

"Alfie!" Tom yelled and slapped the cadet on the back. Alfie turned, his glasses knocked askew by Tom's blow, and eyed the three Polaris members calmly.

"It gives me great pleasure to view your countenances again, Cadets Corbett, Manning, and Astro," he said solemnly, nodding to each one.

Astro twisted his face into a grimace. "What'd he say, Roger?"

"He's happy to see you," Roger translated.

"Well, in that case," beamed Astro, "I'm happy to see you too, Alfie!"

"What's the latest space dope around the Academy, Alfie?" asked Tom. "What's this?" he indicated the paper in Alfie's hand.

"By the sheerest of coincidences I happen to have a copy of your new assignment!" replied Alfie.

Tom, Roger, and Astro looked at each other in surprise.

"Well, come on, spaceman," urged Roger. "Give us the inside info. Where are we going?"

Alfie tucked the paper in his inside pocket and faced Roger. He cleared his throat and spoke in measured tones. "Manning, I have high regard for your personality, your capabilities, and your knowledge, all of which makes you an outstanding cadet. But even you know that I occupy a position of trust as cadet courier for Commander Walters and the administrative staff. I am not at liberty to mention anything that I would have occasion to observe while in the presence of Commander Walters or the staff. Therefore, you will please refrain from questioning me any further regarding the contents of these papers!"

Roger's jaw dropped. "Why, you human calculator, you were the one who brought it up in the first place! I oughta knock off that big head of yours!"

Tom and Astro laughed.

"Lay off, Roger," said Tom. "You ought to know Alfie couldn't talk if he wanted to! We'll just have to wait until Captain Strong is ready to tell us what our next assignment will be!"

By this time the slidewalk had carried them to the front of the main dormitory, and the wide doors were crowded with members of the Space Academy Corps heading in for the evening meal. From all corners of the quadrangle, the slidewalks carried Earthworms in their green uniforms, upper-class cadets in deep blue, enlisted spacemen in scarlet red, and Solar Guard officers in their striking uniforms of black and gold. Chatting and laughing, they all were entering the great building.

The Polaris unit was well known among other cadet units, and they were greeted heartily from all sides. As Astro and Roger joked with various cadet units, forming up in front of the slidestairs leading down to the mess halls, Alfie turned to take a slidestairs going up. Suddenly he stopped, grabbed Tom by the shoulders, and whispered in his ear. Just as abruptly he turned and raced up the ascending slidestairs.

"What was that about?" asked Roger, as Tom stood staring after the little cadet.

"Roger—he—he said our next assignment would be one of the great experiments in space history. Something to be done that—that hasn't ever been done before!"

"Well, blast my jets!" said Astro. "What do you suppose it is?"

"Ahhh," sneered Roger, "I'll bet it's nothing more than taking some guinea pigs to see how they react to