Here begins a chasm which continues for the distance of about a mile and a half. Wonderfully grand are these Walled Rocks of the Au Sable, through, which rushes the river, pent up between literally perpendicular walls, a hundred or more feet in height, and from eleven to sixty or eighty feet apart, generally from twelve to fourteen. The water sometimes rushes smoothly and deeply below, and sometimes falls over obstructions, roaring, and tumbling, and foaming. The turns in the river are very sudden, and there are great cracks and gullies extending from top to base, pillars of rock standing alone or leaning against their companions. Occasionally, looking down one of these clefts, one sees nothing but the rock walls with a foaming, rapid rushing below. At one of these most remarkable points, a rude stairway has been constructed, by which the traveller can descend to the bottom, and, standing by the water's edge, look up to the top of this singular chasm. The walls finally lower, and the river flows out into a broad basin, whence it ere long finds its way into Lake Champlain. The banks are wooded with pines, hemlocks, spruce, arbor vitaae, beech, birch, and basswood, and the ground is covered with ferns, harebells, arbutus, linnaea, mitchella, blue lobelia, and other wild flowers. There is an excellent inn, the Adirondac House, in Keeseville. Our attentive host told us of Professor Agassiz, and the fiery nature of his speculations regarding the probable history of the sandstone, whose strata, laid as at Trenton Falls, horizontally, layer above layer, add such interest and beauty to the stupendous walls, with their unseen, water-covered depths below, and their graceful wreaths of arbor vittae nodding and swaying above. He also told us a tale of the war of 1812, when a bridge, known as the 'High Bridge,' crossed the Au Sable at the narrowest point, some eleven feet in width. A rumor was abroad that the British were about to march up from Plattsburg; whereupon the bridge, consisting of three beams, each nine inches wide, was stripped of its planking. A gentleman had left his home in the morning, and, ignorant of the fate of the bridge, returned quite late at night. Urging his steed forward, it refused to cross the bridge, and not until after repeated castigation would it make the attempt. The crossing was safely accomplished, and the rider suspected nothing amiss until he reached home and was asked how he had come. 'By the High Bridge,' was his reply; whereupon he was informed that the planking had been torn away, and he must have crossed upon a string piece nine inches wide, hanging some hundred feet above the surface of the water. His sensations may be imagined. A venturesome expedition had also been essayed by our host, in the shape of a voyage down the chasm in a boat. We presume he went at high water, when the rapids would be less dangerous.