At about mid-day in the third week of his imprisonment, he cast his eye upon the cavernous and now dusty opening through which the river that watered the plain had been accustomed to find its way. It was broad and open and of considerable height. Into this Behemoth now turned his steps. Its mouth was larger than the inner passage, for time and tempest had worn away the rocks which once guarded it.

As he advanced it diminished, and ere his whole bulk had entered the channel, it became so narrow and confined that he was forced to sink on his knees, in order to make further progress. This labor soon proved vexatious and toilsome, and the Mastodon, willing to force a way where one was not to be found, or to perish in the endeavor, raised himself slowly toward an upright position.

The remnant of his strength proved to be fearful, for, as his broad shoulders pressed upon the rocks above him, the incumbent mountain trembled, and when he had attained his full stature by a last powerful effort, the impending rocks rolled back and forth, and fell with a resounding crash and in great fragments to the earth. The whole cone of the mountain had been loosened from its base, and leaning for a moment, like a lurid cloud, in mid-air, fell into the plain with terrible ruin, bearing down a whole forest of trees and the earth in which they had taken root.

Fortunately for Behemoth— unfortunately for the object of the Mound-builders — the rocks which immediately over-hung Behemoth, though rent in several places, did not give way, but so interlocked and pressed against each other as to form a solid arch over his head and leave him unharmed amid the ruins. Passage through the channel was, however, wholly arrested by the large masses of earth that had fallen into it, and Behemoth finding it vain to attempt to pass farther onward, withdrew.

Part Second, pages 125-126