sacred."

As I walked away, I heard Allenby say, "Take some scrapings from the
inside of the hole, Gonzales. We might be able to determine if anything
is kept in it...."

One of the stumpy, purplish, barrel-type cacti on the ridge had a long
vertical bite out of it ... as if someone had carefully carved out a
narrow U-shaped section from the top down, finishing the bottom of the U
in a neat semicircle. It was as flat and cleancut as the inside surface
of a horseshoe magnet.

I hollered. The others came running. I pointed.

"Oh, my God!" said Allenby. "Another one."

The pulp of the cactus in and around the U-hole was dried and
dead-looking.

Silently Burton used his tape-measure. The hole measured four and
three-eighths inches across. It was eleven inches deep. The semicircular
bottom was about a foot above the ground.

"This ridge," I said, "is about three feet higher than where we landed
the ship. I bet the hole in the rock and the hole in this cactus are on
the same level."

* * * * *

Gonzales said slowly, "This was not done all at once. It is a result of
periodic attacks. Look here and here. These overlapping depressions
along the outer edges of the hole--" he pointed--"on this side of the
cactus. They are the signs of repeated impact. And the scallop effect on
_this_ side, where whatever made the hole emerged. There are juices
still oozing--not at the point of impact, where the plant is desiccated,
but below, where the shock was transmitted--"

A distant shout turned us around. Burton was at the rock, beside the
ship. He was bending down, his eye to the far side of the mysterious
hole.

He looked for another second, then straightened and came toward us at a
lope.

"They line up," he said when he reached us. "The bottom of the hole in
the cactus is right in the middle when you sight through the hole in the
rock."

"As if somebody came around and whacked the cactus regularly," Janus
said, looking around warily.

[Illustration]

"To keep the line of sight through the holes clear?" I wondered. "Why
not just remove the cactus?"

"Religious," Janus explained.

The gauntlet he had discarded lay ignored on the ground, in the shadow
of the cactus. We went on past the ridge toward an outcropping of rock
about a hundred yards farther on. We walked silently, each of us
wondering if what we half-expected would really be there.

It was. In one of the tall, weathered spire