It is malleable, ductile, very very strong, very tough,
especially when alloyed with iron, but those alloys are used only in
very particular work because of iron's rarity."

Indicating the bluish block, Arcot said, "I'd like to identify this
element. May I take it back to the ship and test it?"

"You may, by all means. You will have considerable difficulty getting it
into solution, however. It is attacked only by boiling selenic acid
which, as you must know, dissolves platinum readily. The usual test for
the element is to so dissolve it, oxidize it to an acid, then test with
radium selenate, when a brilliant greenish blue salt is--"

"Test with radium selenate!" Arcot exclaimed. "Why, we have no radium
salts whatever on Earth that we could use for that purpose. Radium is
exceedingly rare!"

"Radium is by no means plentiful here," Tonlos replied, "but we seldom
have to test for morlus, and we have plenty of radium salts for that
purpose. We have never found any other use for radium--it is so active
that it combines with water just as sodium does; it is very soft--a
useless metal, and dangerous to handle. Our chemists have never been
able to understand it--it is always in some kind of reaction no matter
what they do, and still it gives off that very light gas, helium, and a
heavy gas, niton, and an unaccountable amount of heat."

"Your world is vastly different from ours," Arcot commented. He told
Tonlos of the different metals of Earth, the non-metals, and their
occurrence. But try as he would, he could not place the metal Tonlos had
given him.

Morey's arrival interrupted their discussion. He looked very tired, and
very serious. His head ached from his unwonted mental strain, just as
Arcot's had. Briefly Arcot told him what he had learned, concluding with
a question as to why Morey thought the two planets, both members of the
same solar family, should be so different.

"I have an idea," said Morey slowly, "and it doesn't seem _too_ wacky.
As you know, by means of solar photography, astronomers have mapped the
sun, charting the location of the different elements. We've seen
hydrogen, oxygen, silicon and others, and as the sun aged, the elements
must have been mixed up more and more thoroughly. Yet we have seen the
vast areas of single elements. Some of those areas are so vast that they
could easily be the source of an entire world! I wonder if it is not
possible that Earth was thrown off from some deposit rich in