to change course in order to cancel ours out."

He was astonished as the words left his mouth. This was what was needed,
of course. But then he realized that it couldn't be done.

Logan blew a smoke-ring.

"Mechanical computers," he said, "have limits. They're designed to
calculate a trajectory with constant acceleration or no acceleration.
But that's all."

Bors frowned. "What else could there be?"

"Changing acceleration," said Logan condescendingly. "A mechanical
computer can't compute that. But I can."

Bors continued to frown. One part of his mind assured him that the
statement that mechanical computers could not calculate trajectories of
missiles with changing acceleration was incorrect. But the rest of his
mind tried to imagine such a trajectory. He couldn't. In practice, men
do not have to handle the results of variable acceleration as cumulative
effects.

"I think," said Bors carefully, "that if you can do that--"

Logan blew a smoke-ring more perfect than any that had gone before.

"I'll calculate some tables," he said modestly. "You can use them on
your computer-results. Then if you arrange your missiles to change their
acceleration as they go, the Mekinese missiles can't intercept them."

He waved his hand with the grand air of someone assuring a grammar-grade
pupil that multiplication tables were quite reliable and could be used
with confidence. But his eyes fixed themselves on Bors's face. As the
Captain realized the implications of his statement, the eyes of the
Mathematical Talent of Talents, Incorporated shone with gratified
vanity.

"We'll go out in a couple of tin cans," said Bors fiercely, "and try
this out with dummy warheads!"

Gwenlyn said quickly, "Marvelous! Marvelous, Logan!"

"It's nothing," said Logan modestly.

But it was a very great deal. Bors, impatient to try it out,
nevertheless realized that Logan hadn't made the suggestion out of a
brilliant perception of a solution to a problem in ballistics, but
because he thought in terms of mathematical processes. He didn't think
of a new missile operation, but a new kind of computation. And he
reveled in the fact that he had showed off his brilliance.

In the ground-car on the way to the fleet, Bors said helplessly to
Gwenlyn, "I'm not the right man to be the liaison with you people. But
this might make us a pretty costly conquest for Mekin! With luck, we may
trade them ship for ship! They won't miss the ships they lose, but
it