r as we can go upon the meager data we have--considerably farther than
we really are justified in going. We must now try to come to some
conclusion concerning their present activities. If our ideas as to their
natures are even approximately correct, they are waiting, probably
fairly close at hand, until we shall be compelled to release the zone,
no matter how long that period of waiting shall be. They know, of
course, from our small size, that we cannot carry enough copper to
maintain it indefinitely, as they could. Does that sound reasonable?"

"I check you to nineteen decimal places, Mart, and from your ideas I'm
getting surer and surer that we can pull their corks. I can get into
action in a hurry when I have to, and my idea now is to wait until they
relax a trifle, and then slip a fast one over on them. One more bubble
out of the old think-tank and I'll let you off for the day. At what time
will their vigilance be at lowest ebb? That's a poser, I'll admit, but
the answer to it may answer everything--the first shot will, of course,
be the best chance we'll ever have."

"Yes, we should succeed in the first attempt. We have very little
information to guide us in answering that question." He studied the
problem for many minutes before he resumed, "I should say that for a
time they would keep all their rays and other weapons in action against
the zone of force, expecting us to release it immediately. Then, knowing
that they were wasting power uselessly, they would cease attacking, but
would be very watchful, with every eye fastened upon us and with every
weapon ready for instant use. After this period of vigilance, regular
ship's routine would be resumed. Half the force, probably, would go off
duty--for, if they are even remotely like any organic beings with which
we are familiar, they require sleep or its equivalent at intervals. The
men on duty--the normal force, that is--would be doubly careful for a
time. Then habit will assert itself, if we have done nothing to create
suspicion, and their watchfulness will relax to the point of ordinary
careful observation. Toward the end of their watch, because of the
strain of the battle and because of the unusually long period of duty,
they will become careless, and their vigilance will be considerably
below normal. But the exact time of all these things depends entirely
upon their conception of time, concerning which we have no information
whatever. Though it is purely a specula