moon, while almost overhead Mars glowed
brightly.

"There's our goal, Ned," murmured Tom, pointing to the red planet. "I
feel sure that our meteorite came from that far-off world!"

[Illustration: "There's Our Goal, Ned."]

"Granting that it did come from another planet," objected Ned, "I don't
get the reason why you're so sure it came from Mars. There are nine
planets circling the sun, including the earth. Ruling out the sun, it
seems to me that there is but one chance in eight that you are right."

[Illustration: "Nine Planets Circle the Sun."]

"If it were simply a matter of chance, there'd be a lot of weight behind
your argument, Ned. But a lot of other factors enter the problem. I
should say that the only planets where life as we know it might exist
are Mars and Venus. The latter I ruled out, for astronomers have found
that it is forever covered thickly with dense clouds. Thus the
inhabitants, if any, must be ignorant of any world but their own."

"What have people on the planets got to do with the question, anyhow?"
asked Ned. "Huge chunks of metal break off of any heavenly body and go
hurtling through space. The inhabitants don't throw them off!"

[Illustration: Chunks of Metal Rushing Through Space]

"But our meteor was no ordinary one as we have proved already," replied
Tom. "I firmly believe that someone on another planet deliberately fired
that missile into space, hoping it would reach this world. Since
scientists agree that Mars probably is inhabited by a highly intelligent
race, that planet is a reasonable guess."

"Whew!" whistled Ned. "Such ideas are beyond me."

[Illustration: "Someone on Another Planet Fired the Missile."]

As he finished speaking, the boys reached the Swift residence. The
young inventor's father had built the handsome white house many years
before his son was born. Beyond were the several buildings where the
inventions of Tom Swift and his father, Barton Swift, were manufactured.

Of recent years the latter had not been active, but had put the affairs
in the hands of his capable son Tom, ably assisted by Ned Newton. The
older man now spent most of his time writing scientific books and
articles.

[Illustration: The Boys Reached the Swift Residence]

The boys washed as quickly as possible so as not to delay dinner, for
both possessed healthy appetites. Joining Mr. Swift in the library, they
found him and Mr. Damon deep in a game of chess.

"Check!" cried Tom's father tri