ge and we're shooting at a small target, the message
has to be very short or they won't get it all while the beam's on
'em--it isn't as though we were broadcasting. It doesn't need any
address, because nobody but the _Sirius_ can receive it--except possibly
the Jovians. They'll know who's sending it without any signature. It
tells them that Ganymede wants to receive a message on the ultra-band
centering on forty-seven thousandths. Isn't that enough?"

"Maybe. But suppose some of them live right here on Ganymede--you'll
be shooting right through the ground all night--or suppose that even if
they don't live here, that they can find our beam some way? Or suppose
that Brandon hasn't got his machine built yet, or suppose that it isn't
turned on when our beam passes them, or suppose they're asleep then?
A lot of things might happen."

"Not so many, ace--your first objection is the only one that hasn't got
more holes in it than a sieve, so I'll take it first. Since our beam is
only a meter in diameter here and doesn't spread much in the first few
million kilometers, the chance of direct reception by the enemy, even
if they do live here on Ganymede, is infinitesimally small. But I don't
believe that they live here--at least, they certainly didn't land on
this satellite. As you suggest, however, it is conceivable that they may
have detector screens delicate enough to locate our beam at a distance;
but since in all probability that means a distance of hundreds of
thousands of kilometers, I think it highly improbable. We've got to take
the same risk anyway, no matter what we do, whenever we start to use any
kind of driving power, so there's no use worrying about it. As for your
last two objections, I know Brandon and I know Westfall. Brandon will
have receivers built that will take in any wave possible of propagation,
and Westfall, the cautious old egg, will have them running twenty-four
hours a day, with automatic recorders, finders, and everything else that
Brandon can invent--and believe me, sweetheart, that's a lot of stuff!"

"It's wonderful, the way you three men are," replied Nadia thoughtfully,
reading between the lines of Stevens' utterance. "They knew that you
were on the _Arcturus_, of course--and they knew that if you were alive
you'd manage in some way to get in touch with them. And you, away out
here after all this time, are superbly confident that they are expecting
a call from you. That, I think, is one of the fin