?" asked Dorothy. "You didn't tell us anything about a
problem."

"No, I told Mart. I want the best physicist in this entire solar
system--and since there are only one hundred and twenty-five planets
around these seventeen suns, it should be simple to yon phenomenal
brain. In fact, I expect to hear him say 'elementary, my dear Watson,
elementary'!"

"Hardly that, Dick, but I have found out a few things. There are some
eighty planets which are probably habitable for beings like us. Other
things being equal, it seems reasonable to assume that the older the
sun, the longer its planets have been habitable, and therefore the older
and more intelligent the life...."

"'Ha! ha! It was elementary,' says Sherlock." Seaton interrupted.
"You're heading directly at that largest, oldest, and most intelligent
planet, then, I take it, where I can catch me my physicist?"

"Not directly at it, no. I am heading for the place where it will be
when we reach it. That is elementary."

"Ouch! That got to me, Mart, right where I live. I'll be good."

"But you are getting ahead of me, Dick--it is not as simple as you have
assumed from what I have said so far. The Osnomian astronomers have done
wonders in the short time they have had, but their data, particularly on
the planets of the outer suns, is as yet necessarily very incomplete.
Since the furthermost outer sun is probably the oldest, it is the one in
which we are most interested. It has seven planets, four of which are
probably habitable, as far as temperature and atmosphere are concerned.
However, nothing exact is yet known of their masses, motions, or places.
Therefore I have laid our course to intercept the closest one to us, as
nearly as I can from what meager data we have. If it should prove to be
inhabited by intelligent beings, they can probably give us more exact
information concerning their neighboring planets. That is the best I can
do."

"That's a darn fine best, old top--narrowing down to four from a hundred
and twenty-five. Well, until we get there, what to do? Let's sing us a
song, to keep our fearless quartette in good voice."

"Before you do anything," said Margaret seriously, "I would like to know
if you really think there is a chance of defeating those monsters."

* * * * *

"In all seriousness, I do. In fact, I am quite confident of it. If we
had two years, I know that we could lick them cold; and by stepping on
the gas I believ