River below The Dalles, they observed the phenomenon of the submerged forest, which at a low state of water is still conspicuous. They correctly inferred that this indicated a damming up of the River at some recent time. They thought indeed that it could not have been more than twenty years previous. We know, however, that submerged trees or piles, as indicated by remains of old Roman wharves in Britain, may remain intact for hundreds of years. This place on the Columbia is, however, one of the most interesting of its many interesting phenomena. It is evident that within very recent times, geologically speaking, there was a prodigious rock-slide from the mountains which closed the River, producing the cataract of the Cascades and raising the River above, some forty feet.
Here the explorers had their last portage. On the second day of November they reached the foot of the Cascades and perceived the movement of the tide, which made it plain to them that the ocean was near at hand. Yet, in reality, it was much farther than they thought, for the majestic lower River extends one hundred and sixty miles from the foot of the last cataract to the Pacific. It is interesting to notice comments made by the explorers upon the green and fertile islands at the lower end of the Cascades, and that spired and turreted volcanic cliff which they called Beacon Rock, but which we know now as Castle Rock.
The rest of the journey of Lewis and Clark was a calm floating down the tranquil flood of the lower Columbia in the midst of the fog and clouds which at that season of the year generally embrace all objects. On November 7th the mist suddenly broke away before them, the bold mountainous shores vanished in
