"May I?" asked Channing with a smile. He did not mind the interruption; he was used to it in the first place and he had been busy with his pencil in the second place. "Now look, Walt, what happens when you smack a charged condenser across an inductance?" "You generate a damped cycle of the amplitude of the charge on the condenser, and of frequency equal to the L, C, constants of the condenser and inductance. The amplitude decays according to the factor Q, following the equation for decrement--" "Never mind, I've got it here on my whiteboard," smiled Channing, pointing to the tablecloth. "You are right. And the purity of the wave?" "Sinusoidal ... hey! That's it!" Walt jumped to his feet and went to the telephone. "What's 'it'?" asked Arden. "The betatron we have runs off of a five-hundred-volt supply," chuckled Channing. "We can crank that up ten to one without running into any difficulty at all. Five-hundred-volt insulation is peanuts, and the stuff they put on wires nowadays is always good for ten times that just because it wouldn't be economical to try to thin the insulation down so that it only protects five hundred. I'll bet a hat that he would crank the input up to fifty thousand volts without too much sputtering--though I wouldn't know where to lay my lunch hooks on a fifty-thousand-volt condenser of any appreciable capacity. Well, stepping up the rig ten to one will dish us out just shy of a couple of thousand million volts, which, as brother Franks says, is not hay!" * * * * * Walt returned after a minute and said: "Warren's measuring the inductance of the betatron magnet. He'll calculate the value of C required to tune the thing to the right frequency and start to achieve that capacity by mazing up whatever high-voltage condensers we have on the Station. Now, Don, let's calculate how we're going to make the thing mobile." "That's a horse of a different color. We'll have to use electromagnetic deflection. From the constants of the electron stream out of our souped-up Suzy, we'll have to compute the necessary field to deflect such a beam. That'll be terrific, because the electrons are hitting it up at a velocity approaching that of light--maybe a hundred and seventy thousand miles per--and their mass will be something fierce. That again will help to murder Murdoch; increasing mass will help to keep the electrons from being deflected, since it takes more to turn a heavy mass--et cetera, see Newton's laws of inertia for complete statement. Have 'em jerk the D plates out of the cyc and bring the magnet frame down here--to the turret, I mean--and set 'em up on the vertical. We'll use that to run the beam up and down, we can't possibly get one hundred and eighty degree deflection, of course, but we can run the deflection over considerable range. It should be enough to catch a spaceship that is circling the Station. For the horizontal deflection, what have we got?"