"Well, sound recording has come a long way from the tinfoil cylinder that scratched out: 'Mary had a little lamb!' And transportation has come along swell from the days of sliding sledges. You may have the nucleus of an idea, Walt. But I meant its operation instead of its efficiency." "We have an electron gun of super size," explained Walt. "The cathode is a big affair six feet in diameter and capable of emitting a veritable storm of electrons. We accelerate them by means of properly spaced anodes of the proper voltage level, and we focus them into a nice bundle by means of electrostatic lenses--" "Whoah, Tillie, you're talking like the venerable Buck Rogers himself. Say that in words of one cylinder, please," chuckled Arden. "Well, any voltage gradient between electrodes of different voltage acts as a prism, sort of. When you have annular electrodes of the proper size, shape, and voltage difference, they act as a lens." "In other words, the ring-shaped electrodes are electrostatic lenses?" "Nope. It is the space between them. With light or electrons a convex lens will converge the light no matter which direction the light is coming from." "Uh-huh. I see in a sort of vague manner. Now, fellows, go on from there. What's necessary to make this dingbat tick?" "I want to think out loud," said Channing. "That's nothing unusual," said Arden. "Can't we go into Joe's? You can't think without a tablecloth, either." "What I'm thinking is this, Walt. You've been trying to squirt electrons like a fireman runs a hose. Walt, how long do you suppose a sixteen-inch rifle would last if the explosives were constantly replaced and the fire burned constantly?" "Not long," admitted Walt. "A gun is an overloaded machine," said Don. "Even a little one. The life of a gun barrel is measured in seconds; totalling up the time of transit of all the rounds from new gun to worn barrel gives a figure expressed in seconds. Your electron gun, Walt, whether it be fish, flesh, or fowl, must be overloaded for an instant." "Is overload a necessary requirement?" asked Arden. "It seems to me that you might be able to bore a sixteen-inch gun for a twenty-two. What now, little man?" "By the time we get something big enough to do more than knock paint off, we'll have something bigger than a twenty-two," grinned Channing. "I was speaking in terms of available strength versus required punch. In the way that a girder will hold tremendous overloads for brief instants, a gun is overloaded for milliseconds. We'll have a problem--" "O.K., aside from that, have you figured out why I haven't been able to do more than warm anything larger than a house brick?" "Sure," laughed Channing. "What happens in a multi-grid radio tube when the suppressor grid is hanging free?" "Charges negative and blocks the electron stream ... hey! That's it!" "What?" asked Arden.