"Several reasons," Brandon argued stubbornly. "First place, look at the mass of that thing, and remember that the heavier the beam the harder it is to hold it together. Second, there's no evidence that they wander around much in space. If their beams are designed principally for travel upon Jupiter, why should they have any extraordinary range? I say they can't hold that beam forever. We've got a good long lead, and in spite of their higher acceleration, I think we'll be able to keep out of range of their heavy stuff. If so, we'll trace a circle--only one a good deal bigger than the one Amonar suggested--and meet the fleet at a point where that enemy ship will be about out of power." Thus for hours the scientists argued, agreeing upon nothing, while the Vorkulian fortress crept ever closer. At the end of three days of the mad flight, the pursuing space ship was in plain sight, covering hundreds of divisions of the micrometer screens. But now the size of the images was increasing with extreme slowness, and the scientists of the _Sirius_ watched with strained attention the edges of those glowing green pictures. Finally, when the pictured edges were about to cease moving across the finely-ruled lines, Brandon cut down his own acceleration a trifle, and kept on decreasing it at such a rate that the heptagon still crept up, foot by foot. "Hey what's the big idea?" Stevens demanded. "Coax 'em along. If we run away from them they'll probably reverse power and go back home, won't they? Their beam is falling apart fast, but they're still getting so much stuff along it that we couldn't do a thing to stop them. If they think that we're losing power even faster than they are, though, they'll keep after us until their beam's so thin that they'll just be able to stop on it. Then they'll reverse or else go onto their accumulators--reverse, probably, since they'll be a long ways from home by that time. We'll reverse, too, and keep just out of range. Then, when we both have stopped and are about to start back, their beam will be at its minimum and we'll go to work on 'em--foot, horse, and marines. Nobody can run us as ragged as they've been doing and get away with it as long as I'm conscious and stand a chance in the world of hanging one onto their chins in retaliation. I've got a hunch. If it works, we can take those birds alone, and take 'em so they'll _stay_ took. We might as well break up--this is going to be an ordinary job of piloting for a few days, I think. I'm going up and work with the Martians on that hunch. You fellows work out any ideas you want to. Watch 'em close, Mac. Keep kidding 'em along, but don't let them get close enough to puncture us." * * * * *