Coming now to the Cascade Mountains, in Oregon and Washington, we will find in them a number of giant peaks of volcanic origin. The most important of these are in regular order from south to north, as follows: Mt. Pitt, 9,760 feet; Mt. Mazana, 8,223; Mt. Union, 7,881; Mt. Scott, 7,123; Three Sisters, Mt. Jefferson, 10,200, and Mt. Hood, 11,225, in Oregon; Mt. Adams, 9,570; Mt. St. Helen's, 9,750; Mt. Rainier, 14,525, and Mt. Baker in Washington, 10,877. Nearly all these mountains have craters either on their summits or on their sides. They are extinct volcanic mountains, that were, for the most part, thrown up during the Tertiary Geological Period, so that they have all been greatly affected by erosion. One of the most remarkable of the above volcanic mountains is Mt. Mazana, in Oregon. This mountain has on its summit an approximately circular cavity from five to six miles in diameter, that is occupied by a lake of water known as Crater Lake. This lake is 6,239 feet above the level of the sea, and has a depth of 1,975 feet. It is surrounded by nearly vertical walls ranging from 900 to 2,200 feet deep, so that the vast caldera of which this great depression consists has a depth of at least 4,000 feet. Mt. Pitt, situated about sixty miles north of Mt. Shasta, in southern Oregon, has a regularly shaped volcanic cone, and the remnant of a crater at its summit. The Three Sisters and Mt. Jefferson lie to the north of Mt. Pitt. Like the others they are ancient volcanic mountains. But little is accurately known concerning them. Mt. Hood, 11,225 feet high, rises from the crest of the Cascade range in Northwest Oregon, about twenty-five miles south of the Columbia River. Mt. Hood is an exceedingly majestic mountain. At its summit there are only portions of the walls of the original crater. When ascended in 1888, streams of sulphur vapor were escaping from fumaroles on its northeastern slopes, at an elevation of 8,500 feet above the sea. Mt. Adams and Mt. St. Helen's lie to the north of Mt. Hood. Mt. Adams about sixty miles to the north, and beyond this, Mt. St. Helen's. Accurate information concerning the summit of Mt. Adams is still lacking. Mt. St. Helen's in Washington has more of a conical summit. Russell states that according to frontiersmen, St. Helen's has been in a state of activity within the past fifty years. A French-Canadian asserts that the mountain was in actual eruption during the winter of 1841-43, that at this date the light from the volcano was sufficiently bright to enable one to see and pick up a pin in the grass at midnight near his cabin some twenty miles distant. Mt. St. Helen's was ascended in 1889, when fumaroles were found on the northeast side.