man took three right
angles and placed them so that all the angles formed were right
angles, he would discover a fourth dimension. This, however, would
probably be the time dimension, and to travel in time would instantly
be fatal. But with four right angles he could discover a fifth
dimension, and with five right angles he could discover a sixth...."

* * * * *

Tommy Reames put down the paper impatiently.

"Of course" he said brusquely. "I know all that stuff. But up to the
present time nobody has been able to put together even three right
angles, in practise."

Von Holtz had returned to the unscrewing of the wing-nuts. He lifted
off the cover of the dimensoscope.

"It is the thing the Herr Professor did not confide to me," he said
bitterly. "The secret. The one secret! Look in here."

Tommy looked. The objective-glass at the end of the telescope faced a
mirror, which was inclined to its face at an angle of forty-five
degrees. A beam of light from the objective would be reflected to a
second mirror, twisted in a fashion curiously askew. Then the light
would go to a third mirror....

Tommy looked at that third mirror, and instantly his eyes ached. He
closed them and opened them again. Again they stung horribly. It was
exactly the sort of eye-strain which comes of looking through a lens
which does not focus exactly, or through a strange pair of eyeglasses.
He could see the third mirror, but his eyes hurt the instant they
looked upon it, as if that third mirror were distorted in an
impossible fashion. He was forced to draw them away. He could see,
though, that somehow that third mirror would reflect his imaginary
beam of light into a fourth mirror of which he could see only the
edge. He moved his head--and still saw only the edge of a mirror. He
was sure of what he saw, because he could look into the wavy, bluish
translucency all glass shows upon its edge. He could even see the thin
layer of silver backing. But he could not put himself into a position
in which more than the edge of that mirror was visible.

"Good Lord!" said Tommy Reames feverishly. "That mirror--"

"A mirror at forty-five degrees," said Von Holtz precisely, "reflects
light at a right angle. There are four mirrors, and each bends a ray
of light through a right angle which is also a right angle to all the
others. The result is that the dimensoscope looks into what is a fifth
dimension, into which no man ever looke