ern. The top surface of the ground was rolled up into waves like
the sea. The sides of the hole were almost sheer. The naked rock was
exposed for thirty feet. Above the rock could be seen the subsoil, and
then the layer of top soil and vegetation. Dr. Bird was carefully
examining the rock wall.

"What do you make of these, Lassen?" he asked, pointing to a row of
horizontal striations in the rock. The volcanologist studied them.

"They might be water marks but if so they are different from any that
I have seen before," he said doubtfully. "It looks as though some
force had cut the rock away in one sharp stroke."

"Exactly. Notice this yellow powder on the ridges. Water would have
washed it away."

Dr. Bird stepped forward to the wall and idly attempted to pick up a
pinch of the yellow powder he had referred to in his fingers. He gave
an exclamation of surprise as he did so. The powder was evidently fast
to the wall. He drew his knife from his pocket and pried at the stuff.
It fell readily. He scraped again and caught a speck of the falling
powder in his hand. He gave a cry of surprise, for his hand sank as
though borne down by a heavy weight. With an effort he lifted his hand
and examined the substance.

"Come here, Carnes," he said. "Hold your hand up to catch some of this
powder as I scrape it off."

* * * * *

The detective held up his hand. Dr. Bird pried with his knife and a
shower of dull yellow particles fell. Carnes' hand sank as though the
bits of dust had been a lead bar. He placed his other hand under it
and with an effort lifted both hands up a few inches.

"What on earth is this stuff, Doctor?" he cried. "It's as heavy as
lead."

"It's a great deal heavier than lead, Carnesy, old dear. I don't know
what it is. I am inclined to think you did a wise thing when you sent
for me. Lassen, take a look at this stuff. Did you ever run into
anything like it?"

The aged volcanologist shook his head. The yellow powder was something
beyond his ken.

"I have been poking around volcanos all my life," he said, "and I have
seen some queer things come out of the ground--but nothing like that."

Dr. Bird poked tentatively at the substance for a moment, his brow
furrowed in lines of thought. He suddenly threw back his shoulders in
a gesture of decision.

"Send a gang of excavators down here," he cried. "Never mind the power
shovel at present."

* * * *