plainly, a large object which rose from the bottom of the basin. He
advanced eagerly, peering at what seemed to be a sort of dome--like
formation of a lighter color than the rocks about him, and apparently
about ten feet high.

Carefully feeling his way for fear of pitfalls, the captain drew close to
the object, and placed his hand upon it. He believed it to be of stone,
and moving his hand over it, he thought he could feel joints of masonry.
It was clearly a structure built by men. Captain Horn searched his
pockets for a match, but found none, and he hastened back to the cave to
get the lantern, passing, without noticing it, the pail which he had
filled with water. He would have brought the lantern with him when he
first came, but they had no oil except what it contained, and this they
had husbanded for emergencies. But now the captain wanted light--he cared
not what might happen afterwards. In a very short time, with the lantern
in his hand, which lighted up the cave for a considerable distance about
him, the captain again stood at the foot of the subterranean dome.

He walked around it. He raised and lowered his lantern, and examined it
from top to bottom. It was one half a sphere of masonry, built in a
most careful manner, and, to all appearances, as solid as a great stone
ball, half sunken in the ground. Its surface was smooth, excepting for
two lines of protuberances, each a few inches in height, and about a
foot from each other. These rows of little humps were on opposite
sides of the dome, and from the bottom nearly to the top. It was plain
they were intended to serve as rude ladders by which the top of the
mound could be gained.

The captain stepped back, held up his lantern, and gazed in every
direction. He could now see the roof of the cavern, and immediately above