"Oh, you bet!"

"Sure!" They had forgotten how cold and unfriendly the black depths around them had seemed only a short time before. Now it was an enormous room, furnished in splendor, though not yet fully inhabited. It was their own room, to live in, to do with as they liked.

They stood there for quite a long time, enjoying it At last Captain Stone said, "I've had all the sun I can stand for a while. Let's work around back into the shade." He shook his head to dislodge a drop of sweat from his nose.

"We ought to get back to work anyhow."

"I'll help you; we'll get done faster."

The Rolling Stone swung on and outward toward Mars; her crew fell into routine habits. Dr. Stone was handy at weightless cooking, unusually skilful, in fact, from techniques she had picked up during a year's internship in the free-fall research clinic in Earth's station. Meade was not so skilled but very little can be done to ruin breakfast. Her father supervised her hydro­ponics duties, supplementing thereby the course she had had in Luna City High School. Dr. Stone split the care of her least child with his grandmother and used her leisure placidly collating some years of notes for a paper 'On the Cumulative Effects of Marginal Hypoxia."

The twins discovered that mathematics could be even more interesting than they had thought and much more difficult - it required even more 'savvy' than they thought they had (already a generous estimate) and they were forced to stretch their brains. Their father caught up on the back issues of The Reactomotive World and studied his ship's manual but still had plenty of time to coach them and quiz them. Pollux, he discovered, was deficient in the ability to visualise a curve on glancing at ,an equation.

"I don't understand it," he said. "You got good marks in ana­lytical geometry."

Pollux turned red. "What's biting you?" his father demanded.

"Well, Dad, you see it's this way -"

"Go on."

"Well, I didn't exactly get good marks in analyt."

Eh? What is this? You both got top marks; I remember clearly."

"Well, now, you see - Well, we were awfully busy that semester and, well, it seemed logical... " His voice trailed off.

"Out with it! Out with it!"

"Cas took both courses in analyt." Pollux blurted out, "and I took both courses in history. But I did read the book."

"Oh, my!" Roger Stone sighed. "I suppose it's covered by the statute of limitations by this time. Anyhow, you are finding out the hard way that such offences carry their own punishments. When you need it, you don't know it worth a hoot."

"Yessir."

"But an extra hour a day for you, just the same - until you can visualise instantly from the equation a four-coordinate hyper­-surface in a non-Euclidean continuum - standing on your head in a cold shower."

"Yessir."

"Cas, what course did you fudge? Did you read the book?"

"Yes, sir. It was medieval European history, sir."

"Hmm... You're equally culpable, but I'm not too much concerned with any course that does not require a slide rule and tables. You coach your brother."

"Aye aye, sir."

"If you are pinched for time, I'll give you a hand with those broken-down bicycles, though I shouldn't."

The twins pitched into it, hard. At the end of two weeks Roger Stone announced himself satisfied with Pollux's profi­ciency in analytical geometry. They moved on to more rarefied heights... the complex logics of matrix algebra, frozen in beautiful arrays... the tensor calculus that unlocks the atom... the wild and wonderful field equations that make Man king of the universe... the crashing, mind-splitting intuition of Forsyte's Solution that had opened the 21st century and sent mankind another mighty step toward the stars. By the time Mars shone larger in the sky than Earth they had gone beyond the point where their father could reach them; they ploughed on together.

They usually studied together, out of the same book, floating head to head in their bunkroom, one set of feet pointed to celestial south, the other pair to the north. The twins had early gotten into the habit of reading the same book at the same time; as a result either of them could read upside down as easily as in the conventional attitude. While so engaged Pollux said to his brother, "You know, Grandpa, some of this stuff makes me think we ought to go into research rather than business. After all, money isn't everything."

"No," agreed Castor, "there are also stocks, bonds, and patent rights, not to mention real estate and chattels."

"I'm serious.

"We'll do both. I've finished this page; flip the switch when you're ready."

The War God, riding in a slightly different orbit, had been gradually closing on them until she could be seen as a 'star' by naked eye - a variable star that winked out and flared up every sixteen seconds. Through the Stone's coelostat the cause could easily be seen; the War God was tumbling end over end, per­forming one full revolution every thirty-two seconds to provide centrifugal 'artificial gravity' to coddle the tender stomachs of her groundhog passengers. Each half revolution the Sun's rays struck her polished skin at the proper angle to flash a dazzling gleam at the Stone. Through the 'scope the reflection was bright enough to hurt the eyes.

The observation turned out to be both ways. A radio message came in; Hazel printed it and handed it with a straight face to her son: "WAR GOD TO ROLLING STONE - PVT - ROG OLD BOY, I HAVE YOU IN THE SCOPE. WHAT IN SPACE HAVE YOU GOT ON YOU? FUNGUS? OR SEA WEEDS? YOU LOOK LIKE A CHRISI'MAS TREE. P. VANDENBERGH, MASTER."

Captain Stone glared at the message stat. "Why, that fat Dutchman'! I'll "fungus" him. Here, Mother, send this: "Mas­ter to Master - private message: In that drunken tumbling pigeon how do you keep your eye to a scope? Do you enjoy playing nursemaid to a litter of groundhogs? No doubt the dowagers fight over a chance to eat at the captain's table. Fun, I'll bet. R. Stone, Master"."

The answer came back: "ROGER DODGER YOU OLD CODGER, I'VE LIMITED MY TABLE TO FEMALE PASSENGERS CIRCA AGE TWENTY SO I CAN KEEP AN EYE ON THEM - PREFERENCE GIVEN TO BLONDES AROUND FIFTY KILOS MASS. COME OVER FOR DIN­NER. VAN."

Pollux looked out the port, caught the glint on the War God. "Why don't you take him up, Dad? I'll bet I could make it across on my suit jet with one spare oxy bottle."

"Don't be silly. We haven't that much safety line, even at closest approach. Hazel, tell him: "Thanks a million but I've got the prettiest little girl in the system cooking for me right now.""

Meade said, "Me, Daddy? I thought you didn't like my cooking?"

"Don't give yourself airs, snub nose. I mean your mother, of course."

Meade considered this. "But I look like her, don't I?"

"Some. Send it, Hazel."

"RIGHT YOU ARE! MY RESPECTS TO EDITH. "TRUTHFULLY, WHAT IS THAT STUFF? SHALL I SEND OVER WEEDKILLER, OR BARNACLE REMOVER? OR COULD WE BEAT IT TO DEATH WITH A STICK?"

"Why not tell him, Dad?" Castor inquired

"Very well, I will, send: "Bicycles: want to buy one?""

To their surprise Captain Vandenbergh answered:

"MAYBE. GOT A RALEIGH "SANDMAN"?"

"Tell him, "Yes!"

"Pollux put in. "A-number-one condition and brand-new tires. A bargain."

"Slow up there," his father interrupted. "I've seen your load. If you've got a bike in first-class condition, Raleigh or any other make, you've got it well hidden."

"Aw, Dad, it will be - by the time we deliver."

"What do you suppose he wants a bicycle for, dear?" Dr. Stone asked. "Prospecting? Surely not."

"Probably just sightseeing. All right, Hazel, you can send it - but mind you, boys, I'll inspect that vehicle-myself; Van trusts me."