“But,” said the Medical Man, staring hard at a coal in the fire, “if
Time is really only a fourth dimension of Space, why is it, and why has
it always been, regarded as something different? And why cannot we move
about in Time as we move about in the other dimensions of Space?”

The Time Traveller smiled. “Are you so sure we can move freely in
Space? Right and left we can go, backward and forward freely enough,
and men always have done so. I admit we move freely in two dimensions.
But how about up and down? Gravitation limits us there.”

“Not exactly,” said the Medical Man. “There are balloons.”

“But before the balloons, save for spasmodic jumping and the
inequalities of the surface, man had no freedom of vertical movement.”

“Still they could move a little up and down,” said the Medical Man.

“Easier, far easier down than up.”

“And you cannot move at all in Time, you cannot get away from the
present moment.”

“My dear sir, that is just where you are wrong. That is just where the
whole world has gone wrong. We are always getting away from the present
moment. Our mental existences, which are immaterial and have no
dimensions, are passing along the Time-Dimension with a uniform
velocity from the cradle to the grave. Just as we should travel _down_
if we began our existence fifty miles above the earth’s surface.”

“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_?”

“The experiment!” cried Filby, who was getting brain-weary.

“Let’s see your experiment anyhow,” said the Psychologist, “though it’s
all humbug, you know.”

The Time Traveller smiled round at us. Then, still smiling faintly, and
with his hands deep in his trousers pockets, he walked slowly out of
the room, and we heard his slippers shuffling down the long passage to
his laboratory.

The Psychologist looked at us. “I wonder what he’s got?”

“Some sleight-of-hand trick or other,” said the Medical Man, and Filby
tried to tell us about a conjuror he had seen at Burslem, but before he
had finished his preface the Time Traveller came back, and Filby’s
anecdote collapsed.

II.
The Machine