ond of _time_
passes, is impelled by the force of nature to be in a
_different place_. This involves motion. A small change in
the first second. Then the current alters it progressively
faster. The change, of necessity, is progressively greater,
the motion more rapid.

And this, controlled as to direction, became transportation.
The determination of direction at first thought seems
amazingly intricate. In effect, that was not so. With
space-time factors set as a destination, i. e., the place
where the vehicle must end its change at a certain time, all
the intermediate changes become automatic. With every
passing second it must be at a reconcilable place--the
direction of its passage perforce being the shortest path
between the two.

With this in mind, the transition from one world to another
becomes more readily understandable. No _natural_ change of
space is involved, merely the change of the state of matter.
It was the same change as that which carried the vehicles
into a shadowy borderland, and then pushed further into new
dimensional realms.

The green light-beam weapons were merely another application
of the same principle. The characteristics of the green
light current, touching organic matter, altered the
vibratory rate of what was struck to coincide with the
light. A solid cake of ice under a blow-torch becomes steam
by the same principle. The light-beams were swift and
violent in their action. The change in them was progressive
also--but it was so swiftly violent a change that nothing
living could survive the shock of the enforced transition.

* * * * *

There was little to see during this strange flight. Outside our
windows gray shadows drifted swiftly past--a shadowy, ghostly
landscape of gray rocks. Sometimes it was below us, so that we
seemed in an airship winging above it. Then abruptly it would rise
over us and we plunged into it as though it were a mere light-image,
a mirage.

Hours passed. For the most part the shadowy void seemed a jagged
mountainous terrain, a barren waste. There were great plateau
uplands, one of which rose seemingly thousands of feet over us. And
there was perhaps an hour of time when the surface of the world had
dropped far away, so far down that it was gone in the distance. Like
a projectile we sped level, unswerving. And at