CHAPTER XXXI.
GEOLOGICAL FORMATION OF OREGON.
We owe to Rev. Thomas Condon, of Dalles City, all our real information upon the geology of Oregon, as well as many notes upon its mineralogy. That which we were able to observe for ourselves only corroborated his views. According to Mr. Condon, the Rocky Mountains once formed the western breakwater of the continent, as the Coast Mountains now do. They were forced up by the subsidence of the ocean-bottom, and the consequent upfolding of the earth's crust. The upheaval occurred near the shore-line, but left a narrow strip of the old sea-bed east of the Rocky Range; enough to prove that the upheaval occurred in the Cretaceous period. A large body of salt water was thus isolated, which gradually, by natural drainage, became brackish only, and finally quite fresh. This change is also proven by the nature of the deposits.
After a long interval of quiet, another upheaval took place, occasioned, like the first, by a subsidence of the ocean-bed. At this second folding of the earth's crust, the Cascades and Blue Mountains were forced up, and once more a large body of sea-water was divided off from the ocean, to form great salt lakes, which gradually became fresh. The Blue Mountains formed an island, separating the northern portion of these waters from the southern, which were
