e discovered is a way not only of moving back into the past,
but also of making our own choice of spatial references while we do it,
and of changing our spatial anchor at will.

"For example, to reach this planet, I went back far enough, using Earth
as the spatial referent, to move with Earth a little more than a third
of the way around this spiral nebula that is our Galaxy. Then I shifted
my frame of reference to that of the group of galaxies of which ours is
such a distinguished member.

"Then of course, as I continued to move in time, the whole Galaxy moved
spatially with reference to my own position. At the proper instant I
shifted again, to the reference frame of this Galaxy itself. Then I was
stationary in the Galaxy, and as I continued time traveling, your own
mighty sun moved toward me as the Galaxy revolved. I chose a point where
there was a time intersection of your planet's position and my own. When
you got there, I just changed to the reference plane of this planet I'm
on now, and then came on back with it to the present. So here I am. It
was a long way around to cover a net distance of 26 light-years, but it
was really very simple.

"And there's no danger of meeting myself, or getting into any
anachronistic situation. As you probably know, theory shows that these
are excluded times for me, as is the future--I can't stop in them."

"Are you sure that you haven't given us a little too much information
for your own safety?" asked Ffallk softly.

"Not at all. We were enormously lucky to have learned how to control
spatial reference frames ourselves. I doubt if you could do it in
another two million years." Crownwall rose to his feet. "And now, Your
Effulgence, I think it's about time I went back to my ship and drove it
home to Earth to make my report, so we can pick up those bombs and start
making arrangements."

"Excellent," said Ffallk. "I'd better escort you; my people don't like
strangers much."

"I'd noticed that," Crownwall commented drily.

"Since this is a very important occasion, I think it best that we make
this a Procession of Full Ceremony. It's a bother, but the proprieties
have to be observed."

* * * * *

Ggaran stepped out into the broad corridor and whistled a shrill
two-tone note, using both his speaking and his eating orifices. A cohort
of troops, pikes at the ready and bows strapped to their backs, leaped
forward and formed a double line leading fro