"That would do it," said Channing thoughtfully. "But I don't think I'd know how to modulate a VanDerGraf. A betatron would be the thing. You can modulate that, sort of, by keying the input. She'd give out with hundred-and-fifty-cycle stuff, but so what? We made the _Empress of Kolain_ sit up and say uncle on hundred-cycle stuff. How much of a trick is it to clear the observation dome from the top?" "What do you intend to do?" "Well, we've got a long, hollow tube in this ship. Knock out the faceted dome above, and we can rig us up a huge electron gun. We'll turn the ship to point at the Station and beam 'em a bouquet of electrons." "How're you going to do that?" "Not too tough, I don't think. Down here," and Channing began to trace on the tablecloth, "we'll put us a hot cathode. About this level we'll hang the first anode, and at this level we'll put the second anode. Here'll be an acceleration electrode, and up near the top we'll put a series of focusing anodes. We'll tap in to the driver-tube supply and take off voltages to suit us. Might use a tube at that, but the conversion to make an honest electron gun out of it would disrupt our power, and then it would be impossible to make a driver out of it again without recourse to a machine shop." "How are you going to make electrodes?" "We'll use the annular gratings that run around the central well at each level," said Channing. "We'll have a crew of men cut 'em free and insulate the resulting rings with something. Got anything?" "There is a shipment of methyl-methacrylate rods for the Venus Power Co. in Hold 17," said the cargo master. "Fine," said Channing. "What size?" "Three inches by six feet." "It'll be tricky work, and you'll have to wait until your cut edge has cooled before you hook on the rods," mused Don. "But that's the ticket." "Which floors do you want?" "Have you got a scale drawing of the _Solar Queen_?" "Sure." "Then this is where my tablecloth artistry falls flat. The focusing of an electron beam depends upon the electrode spacing and the voltage. Since our voltage is fixed if we take it from the driver electrodes, we'll have to do some mighty fine figuring. I'll need that scale drawing." * * * * * Channing's tablecloth engineering was not completely wasted. By the time the scale drawing was placed before him, Channing had half of the table filled with equations. He studied the drawing, and selected the levels which were to serve as electrodes. He handed the drawing to Hadley, and the power engineer began to issue instructions to his gang. Then the central well began to swarm with spacesuited men who bore cutting torches. Hot sparks danced from the cut girders that held the floorings, and at the same time, a crew of men were running cables from the various levels to the instrument room. More hours passed while the circular sections were insulated with the plastic rods.