"I'm not going to aim at Tellus. I'm shooting at Brandon, and he's never there for more than a week or two at a stretch. They're prowling around out in space somewhere almost all the time." "Then how can you possibly hope to hit them?" "It may be quite a job of hunting, but not as bad as you might think. They probably aren't much, if any, outside the orbit of Mars, and they usually stay within a couple of million kilometers or so of the Ecliptic, so we'll start at the sun and shoot our beam in a spiral to cover that field. We ought to be able to hit them inside of twelve hours, but if we don't, we'll widen our spiral and keep on trying until we do hit them." "Heavens, Steve! Are you planning on telegraphing steadily for days at a time?" "Sure, but not by hand, of course--I'll have an automatic sender and automatic pointers." Stevens had at his command a very complete machine-shop, he had an ample supply of power, and all that remained for him to do was to assemble the parts which he had built during the long journey from Titan to Ganymede. Therefore, at sunrise of the designated day, he was ready, and, with Nadia hanging breathless over his shoulder, he closed the switch, a toothed wheel engaged a delicate interrupter, and a light sounder began its strident chatter. "Ganymede point oh four seven ganymede point oh four seven ganymede point oh four seven..." endlessly the message was poured out into the ether, carried by a tight beam of ultra-vibrations and driven by forces sufficient to propel it well beyond the opposite limits of the orbit of Mars. "What does it say? I can't read code." Stevens translated the brief message, but Nadia remained unimpressed. "But it doesn't say anything!" she protested. "It isn't addressed to anybody, it isn't signed--it doesn't tell anybody anything about anything." "It's all there, ace. You see, since the beam is moving sidewise very rapidly at that range 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."