l odor. Hundreds of short, clawed legs slithered on the rocks under
a long sinuous body. Then it seemed to leap into the air again. Webs
grew taut between the legs, strumming as they caught a strong uphill
wind. Again it turned to the attack, and missed them. This time
Forepaugh was ready for it. He shot at it with his flash pistol.

* * * * *

Nothing happened. The fog made accurate shooting impossible, and the
gun lacked its former power. The web serpent continued to course back
and forth over their heads.

"Guess we'd better run for it," Forepaugh murmured.

"Go 'head!"

They cautiously left their places of concealment. Instantly the
serpent was down again, persistent if inaccurate. It struck the place
of their first concealment and missed them.

"Run!"

They extended their weary muscles to the utmost, but it was soon
apparent that they could not escape long. A rock wall in their path
saved them.

"Hole!" the Martian gasped.

Forepaugh followed him into the rocky cleft. There was a strong draft
of dry air, and it would have been next to impossible to hold the
Martian back, so Forepaugh allowed him to lead on toward the source of
the draft. As long as it led into the mountains he didn't care.

The natural passageway was untenanted. Evidently its coolness and
dryness made it untenable for most of Inra's humidity and heat loving
life. Yet the floor was so smooth that it must have been artificially
leveled. Faint illumination was provided by the rocks themselves. They
appeared to be covered by some microscopic phosphorescent vegetation.

After hundreds of twists and turns and interminable straight galleries
the cleft turned more sharply upward, and they had a period of stiff
climbing. They must have gone several miles and climbed at least
20,000 feet. The air became noticeably thin, which only exhilarated
Gunga, but slowed the Earth man down. But at last they came to the end
of the cleft. They could go no further, but above them, at least 500
feet higher, they saw a round patch of sky, miraculously bright blue
sky!

"A pipe!" Forepaugh cried.

He had often heard of these mysterious, almost fabulous structures
sometimes reported by passing travelers. Straight and true, smooth as
glass and apparently immune to the elements, they had been
occasionally seen standing on the very tops of the highest
mountains--seen for a few moments only before they were hidden again
by the clou