he slope was reached, and the combined lights of the two
pocket-lamps showed them that they had reached a tiny chamber
irregularly hewn in the living rock. This also was less than four feet
high, but its jagged floor being level, they were enabled to pause
here for a while.

"Do you notice something unfamiliar in the smell of the place?"

Dr. Cairn was the speaker. Sime nodded, wiping the perspiration from
his face the while.

"It was bad enough when I came here before," he said hoarsely. "It is
terrible work for a heavy man. But to-night it seems to be reeking. I
have smelt nothing like it in my life."

"Correct," replied Dr. Cairn grimly. "I trust that, once clear of this
place, you will never smell it again."

"What is it?"

"It is the _incense_," was the reply. "Come! The worst of our task is
before us yet."

The continuation of the passage now showed as an opening no more than
fifteen to seventeen inches high. It was necessary, therefore, to lie
prone upon the rubbish of the floor, and to proceed serpent fashion;
one could not even employ one's knees, so low was the roof, but was
compelled to progress by clutching at the irregularities in the wall,
and by digging the elbows into the splintered stones one crawled upon!

For three yards or so they proceeded thus. Then Dr. Cairn lay suddenly
still.

"What is it?" whispered Sime.

A threat of panic was in his voice. He dared not conjecture what would
happen if either should be overcome in that evil-smelling burrow, deep
in the bowels of the ancient building. At that moment it seemed to
him, absurdly enough, that the weight of the giant pile rested upon
his back, was crushing him, pressing the life out from his body as he
lay there prone, with his eyes fixed upon the rubber soles of Dr.
Cairn's shoes, directly in front of him.

But softly came a reply:

"Do not speak again! Proceed as quietly as possible, and pray heaven
we are not expected!"

Sime understood. With a malignant enemy before them, this hole in the
rock through which they crawled was a certain death-trap. He thought
of the headless bats and of how he, in crawling out into the shaft
ahead, must lay himself open to a similar fate!

Dr. Cairn moved slowly onward. Despite their anxiety to avoid noise,
neither he nor his companion could control their heavy breathing. Both
were panting for air. The temperature was now deathly. A candle would
scarcely have burnt in the vitiated air; and above t