rs, it
is still some five hundred and fifty million kilometers away, so you
can form some idea as to how far it is from our nearest planet now.
No, if we expect to get back under our own power, we've got to break away
pretty quick--these lifeboats have very little accumulator capacity, and
the receptors are useless above about three hundred million
kilometers...."

"But it'll take us a long time to go that far, won't it?"

"Not very. Our own ships, using only the acceleration of gravity, and
both plus and minus at that, make the better than four hundred million
kilometers of the long route to Mars in five days. These birds are using
almost that much acceleration, and I don't see how they do it. They must
have a tractor ray. Brandon claimed that such a thing was theoretically
possible, but Westfall and I couldn't see it. We ragged him about it a
lot--and he was right. I thought, of course, they'd drift with us, but
they are using power steadily. They've got _some_ system!"

"Suppose they could be using intra-atomic energy? We were taught that it
was impossible, but you've shattered a lot of my knowledge today."

"I wouldn't want to say definitely that it is absolutely impossible,
but the deeper we go into that line, the more unlikely intra-atomic
energy power-plants become. No, they've got a real power-transmission
system--one that can hold a tight beam together a lot farther than
anything we have been able to develop, that's all. Well, we've given
them quite a lot of time to get over any suspicion of us, let's see
if we can sneak away from them."

* * * * *

By short and infrequent applications of power to the dirigible
projectors of the life-boat, Stevens slowly shifted the position of
the fragment which bore their craft until it was well clear of the
other components of the mass of wreckage. He then exerted a very small
retarding force, so that their bit would lag behind the procession, as
though it had accidently been separated. But the crew of the captor was
alert, and no sooner did a clear space show itself between them and the
mass than a ray picked them up and herded them back into place. Stevens
then nudged other pieces so that they fell out, only to see them also
rounded up. Hour after hour he kept trying--doing nothing sufficiently
energetic to create any suspicion, but attempting everything he could
think of that offered any chance of escape from the clutches of their
cap