means of judging the angle of
the curve.

A narrow white stream of light, it flung through our window-oval,
forward under the dome and through the bow dome bullseye, into space.
I saw the men on the deck spring into sudden alertness with the
realization we were using it. The bow lookout on the forward
observation bridge crouched at his 'scope-finder to help us search.

From the control turret came an audiphone buzz, and Drac's voice: "Am
I headed right? The swing is almost completed."

"Finish the job and don't bother me now."

I bent over the field-mirror of the projector. On its glowing ten-inch
grid the shifting image of my range was visible, a curving, brilliant
limb of the Moon, with the sunlight on the jagged mountain peaks;
everywhere else was the black firmament and the blazing dots of stars.

Grantline crouched beside me. "I'll work the amplifiers. Going to
spread it much, Gregg?"

"Yes. A full spread first. We're in no mood for a detailed narrow
search."

I gradually widened the light. Three feet here at its source, it
spread in a great widening arc. With the naked eye we could see its
white radiance, fan-shaped as an edge of it fell upon the Moon. And
though optically it was not apparent, the elliptical curve of it was
rounding the Moon, disclosing the hidden starfield to our
instruments.

"Nothing yet?" I murmured.

"No."

"I'll try a narrower spread and less curve."

Grantline was searching the magnified images on the series of
amplifier grids. There was nothing. For an hour we worked; then
suddenly Grantline cried: "Gregg! Wait! Hold it!"

I tensed, stricken. I held the angle and the spread of light steady.

"Two seconds of arc, east; try that. The damned thing is shifting." He
gripped me. "It's at the eastern edge of the field; it shifts off. It
must be in rapid motion."

Then I saw it, a mere moving dot of black; but suddenly it clarified.
I saw a dot which I could imagine was a shape with discs along its
edge, moving with high velocity. Grantline was shifting our field to
hold it.

"Got it, Gregg. By God, that's it! Now we'll see."

Then presently we saw that from its bow a very faint radiant beam was
streaming. Beside me I heard Grantline gasp, "Gregg, am I crazy or is
that bow beacon like the light-beam planted in Greater New York?"

There did seem to be a similarity, but thought of it abruptly was
swept from my mind. Our cubby was alive with signals. Both the bow and
the ster