Page:The Columbia River - Its History, Its Myths, Its Scenery Its Commerce.djvu/467

Rh feature of Columbia River scenery for these fifty miles. Mitchell's Point, Shell Mountain, Wind Mountain, Bald Mountain, and Mt. Defiance are the first group. The lowest of the group attains an elevation of nearly two thousand feet, almost perpendicular, while at the summit of the crags rise a thousand feet higher yet long grassy slopes alternating with splendid forests.

As we near the Cascades we note another curious phenomenon. This is the sunken forest on either side. At low water these old tree trunks become very observable, and their general appearance suggests at once that they are the remains of a former forest submerged by a permanent rise in the river. This explanation is confirmed by the fact that from The Dalles to the Cascades the river is very deep and sluggish. When we reach the Cascades a third fact is revealed and that is that at the chief cataract the river bank is continually sliding into the river. Trees are thrown down by this slow sliding process, railroad tracks require frequent adjustment, and on clear, still nights there is sometimes heard a grinding sound, while a tremor from the subterranean regions seems to indicate that the upper stratum is sliding over the lower toward the river. In fact, the mighty force of the stream is all the time eating into the bank and gradually drawing it down.

From those and other indications the conclusion has been drawn that some prodigious avalanche of rock at a not long distant time dammed the river at this point, creating the present Cascades and raising the water above so as to submerge the forest, whose remains now attract the attention of the observer at the low stage of water.