Bors couldn't quite believe it. The distance between the two stars was a rounded-off number, of course. The relative proper motion of the two stars had a large plus-or-minus bugger factor. The time-lapse due to distance had a presumed correction and there was a considerable probable error in the speed of translation of the ship during overdrive. It was a moderately complicated equation, and the computation of the probable error was especially tricky. Bors stared at it, and then stared at Logan.
"That's the answer to what you have written there," said Logan condescendingly, "but your figures are off. I've been talking to your computer men. They've given me the log figures on past overdrive jumps and the observed errors on arrival. They're systematic. I noticed it at once."
"There's a source of consistent error," Logan said patiently. "I found the values to correct it, then I found the source. It's in your overdrive speed."
Bors blinked. Speed in overdrive could not be computed exactly. The approximation was very close--within a fraction of a tenth of one per cent--but when the distance traveled was light-years the uncertainty piled up.
"If you use these figures," said Logan complacently--and he scribbled figures swiftly--"you'll get it really accurate."
Having finished writing the equation, he wrote the solution. Bors asked suspicious questions. Logan answered absently. He knew nothing about overdrive. He didn't understand anything but numbers and he didn't know how he did what he did with them. But he'd worked backward from observed errors in calculation and found a way to keep them out of the answer. And he'd done it all in his head. It was unbelievable--yet Bors believed.
"I'll try your figures," he said. "Thanks."
Logan went proudly away, past an orderly bringing cups of coffee to the control room. Bors aimed the ship according to the calculation Logan had given him, scrupulously setting the breakout timer to the exact figure listed.
He was still uncomfortable about the destruction of the Mekinese cruiser when he said curtly, "Overdrive coming!" He'd have preferred a more sportsmanlike type of warfare. He faced the old, deplorable fact that fighting men had had to adjust to throughout the ages; one can fight an honorable enemy honorably, but against some men scruples count as handicaps.