ing back for any length of time, any more than a savage or an animal has of staying six feet above the ground. But a civilised man is better off than the savage in this respect. He can go up against gravitation in a balloon, and why should he not hope that ultimately he may be able to stop or accelerate his drift along the Time-Dimension, or even turn about and travel the other way?"
"Oh, this," began Filby, "is all———"
"Why not?" said the Time Traveller.
"It's against reason," said Filby.
"What reason?" said the Time Traveller.
"You can show black is white by argument," said Filby, "but you will never convince me."
"Possibly not," said the Time Traveller. "But now you begin to see the object of my investigations into the geometry of Four Dimensions. Long ago I had a vague inkling of a machine———"
"To travel through Time!" exclaimed the Very Young Man.
"That shall travel indifferently in any direction of Space and Time, as the driver determines."
Filby contented himself with laughter.
"But I have experimental verification," said the Time Traveller.
"It would be remarkably convenient for the historian," the Psychologist suggested. "One might travel back and verify the accepted account of the Battle of Hastings, for instance!"
"Don't you think you would attract attention?" said the Medical Man. "Our ancestors had no great tolerance for anachronisms."
8
