days and nights are less than ten minutes in duration."

"Well, is it barren, then? No minerals of value? No vegetation?"

"The spectroscope shows plenty of metals, including heavy radium
deposits. The vegetation is as luxuriant as that of semi-tropic Earth."

"Then why in the name of Betelguese," said Harley, exasperated, "won't
you sell the place to me? It's exactly what I've been looking for, and
what I'd despaired of finding at my price."

"I'm forbidden to tell why it isn't for sale," said the executive,
starting to float off. "It might hurt our business, reputation if the
truth about that bit of our celestial properties became widely
known--Oh, disintegrate it all! Why wasn't the thing erased from the
chart weeks ago!"

"Wait a minute." Harley caught his arm and detained him. "You've gone
too far to back out now. I'm too eager to find some such place as your
Z-40 to be thrown off the subject like a child. _Why_ isn't it for
sale?"

The man tightened his lips as though to refuse to answer, then shrugged.

"I'll tell you," he said at last. "But I beg of you to keep it
confidential. If some of our investors on neighboring asteroids ever
found out about the peril adjoining them on Z-40, they'd probably insist
on having their money back."

He led the way to a more secluded spot under the big dome, and spoke in
a low tone, with many a glance over his shoulder to see if anyone were
within earshot.

"Z-40 is an exceptionally fine bit of property. It is commodious; about
twenty miles in diameter. Its internal heat is such that it has a
delightful climate in spite of the extreme rarity of atmosphere common
to even the best of asteroids. It has a small lake; in fact it has about
everything a man could want. Yet, as I said, it is uninhabitable."

His voice sank still lower.

"You see, sir, there's already a tenant on that sphere, a tenant that
was in possession long before the Celestial Developments Company was
organized. And it's a tenant that can't be bought off or reasoned with.
It's some sort of beast, powerful, ferocious, that makes it certain
death for a man to try to land there."

"A beast?" echoed Harley. "What kind of a beast?"

"We don't know. In fact we hardly even know what it looks like. But from
what little has been seen of it, it's clear that it is like no other
specimen known to universal science. It's something enormous, some freak
of animal creation that seems invulnerable to man's smaller wea