"You talk like Burbank," said Thomas, mentioning a sore spot of some months past. "You think a mass detector would work at this distance? Nuts, fellow. It might, if there were nothing else in the place to interfere. But you want to shoot out near Mars. Mars is on the other side of the Sun--an Evening Star to anyone on Terra. You want us to shoot a slap-happy beam like the mass detector out past Sol; and then a hundred and forty million miles beyond in the faint hope that you can triangulate upon a little mite of matter; a stinking six hundred-odd feet of aluminum hull mostly filled with air and some machinery and so on. Brother, what do you think all the rest of the planets will do to your little piddling beam? Retract, or perhaps abrogate the law of universal gravitation?" "Crushed," said Franks with a sorry attempt at a smile. "_Phew!_" agreed Channing. "Maybe I should know more about mass detectors." "Forget it," said Charles. "The only thing that mass detectors are any good for is to conjure up beautiful bubble dreams, which anybody who knows about 'em can break with the cold point of icy logic." "What would you do?" asked Channing. "Darned if I know. We might flash 'em with a big mirror--if we had a big mirror and they weren't heading right into the Sun." "Let's see," mused Franks, making tabulations on the tablecloth. "They're a couple of hundred million miles away. In order that your mirror present a recognizable disk, it should be about twice the diameter of Venus as seen from Terra. That's eight thousand miles in--at best visibility--say, eighty million or a thousand-to-one ratio. The _Empress of Kolain_ is heading at us from some two hundred million, so at a thousand-to-one ratio our mirror would have to be twenty thousand miles across. Some mirror!" Don tipped Walt's beer over the edge of the table, and while the other man was busy mopping up and muttering unprintables, Don said to Thomas: "This is serious and it isn't. Nobody's going to lose their skin if we don't, but a problem has been put to us and we're going to crack it if we have to skin our teeth to do it." "You can't calculate their position?" "Sure. Within a couple of thousand miles we can. That isn't close enough." "No, it isn't," agreed Chuck. * * * * * Silence fell for a minute. It was broken by Arden, who came in waving a telegram. She sat down and appropriated Channing's glass, which had not been touched. Don opened the sheet and read: "Have received confirmation of your effort. I repeat, spare no expense!" It was signed: "Williams, Interplanet." "Does that letter offer mean anything to you?" asked Arden. "Sure," agreed Don. "But at the time we're stumped. Should we be doing something?" "Anything, I should think, would be better than what you're doing at present. Or does that dinner-and-beer come under the term 'Expenses'?"