“But the great difficulty is this,” interrupted the Psychologist. ’You can move about in all directions of Space, but you cannot move about in Time.”

“That is the germ of my great discovery. But you are wrong to say that we cannot move about in Time. For instance, if I am recalling an incident very vividly I go back to the instant of its occurrence: I become absent-minded, as you say. I jump back for a moment. Of course we have no means of staying 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.”

“One might get one’s Greek from the very lips of Homer and Plato,” the Very Young Man thought.

“In which case they would certainly plough you for the Little-go. The German scholars have improved Greek so much.”

“Then there is the future,” said the Very Young Man. “Just think! One might invest all one’s money, leave it to accumulate at interest, and hurry on ahead!”

“To discover a society,” said I, “erected on a strictly communistic basis.”

“Of all the wild extravagant theories!” began the Psychologist.

“Yes, so it seemed to me, and so I never talked of it until—”

“Experimental verification!” cried I. “You are going to verify that?”