volcanic nature of this enormous excavation was confirmed on all
sides, and I pointed it out to my companions.

"Picture to yourselves," said I, "what this crater must have been when
filled with boiling lava, and when the level of the incandescent liquid
rose to the orifice of the mountain, as though melted on the top of a
hot plate."

"I can picture it perfectly," said Conseil. "But, sir, will you tell
me why the Great Architect has suspended operations, and how it is that
the furnace is replaced by the quiet waters of the lake?"

"Most probably, Conseil, because some convulsion beneath the ocean
produced that very opening which has served as a passage for the
Nautilus. Then the waters of the Atlantic rushed into the interior of
the mountain. There must have been a terrible struggle between the two
elements, a struggle which ended in the victory of Neptune. But many
ages have run out since then, and the submerged volcano is now a
peaceable grotto."

"Very well," replied Ned Land; "I accept the explanation, sir; but, in
our own interests, I regret that the opening of which you speak was not
made above the level of the sea."

"But, friend Ned," said Conseil, "if the passage had not been under the
sea, the Nautilus could not have gone through it."

We continued ascending. The steps became more and more perpendicular
and narrow. Deep excavations, which we were obliged to cross, cut them
here and there; sloping masses had to be turned. We slid upon our
knees and crawled along. But Conseil's dexterity and the Canadian's
strength surmounted all obstacles. At a height of about 31 feet the
nature of the ground changed without becoming more practicable. To the
conglomerate and trachyte succeeded black basalt, the first dispread in
layers full of bubbles, the latter forming regular prisms, placed like
a colonnade supporting the spring of the immense vault, an admirable
specimen of natural architecture. Between the blocks of basalt wound
long streams of lava, long since grown cold, encrusted with bituminous
rays; and in some places there were spread large carpets of sulphur. A
more powerful light shone through the upper crater, shedding a vague
glimmer over these volcanic depressions for ever buried in the bosom of
this extinguished mountain. But our upward march was soon stopped at a
height of about two hundred and fifty feet by impassable obstacles.
There was a complete vaulted arch overhanging us, and our as