There are several fine, sharp peaks in the Olympics that have never been scaled, the highest of which, Mount Olympus, rises 8,150 feet above the sea. Owing to the excessive humidity and other favourable climatic conditions, these mountains are clothed with magnificent forests up to an elevation of about 7,000 feet. On account of the ruggedness of the country, the extreme density of the tangled undergrowth, and the obstructions formed by the fallen moss- and lichen-covered trees, this region is extremely difficult to traverse, and to-day is the least known of the continental portion of the United States. On the north the excessively rugged Olympic peninsula is bordered by a deep, broad fiord known as the Strait of Fuca. To the north of this formerly ice-filled channel lies Vancouver Island, the central and northern portion of which is mountainous. The highest summit on the island rises about 7,500 feet above the sea, and a considerable area in its central part has an elevation of over 2,000 feet. The Olympics, together with the mountains of Vancouver and Queen Charlotte Islands, and the northern extension of the same belt, embraced in part within the mainland of British Columbia and southeastern Alaska, have been termed the "Vancouver Mountains" by Canadian geographers. The northern boundary of this mountain system, justly named in honour of the celebrated English explorer who mapped large portions of the northwest coast about a century since, remains indefinite, and cannot be determined until geologists have made more thorough explorations of the land it occupies. The leading geographical features of this region, as remarked in a preceding chapter, are due to the deep dissection, by streams and glaciers, of an elevated table-land. When the ice-streams melted, the sea was permitted to enter the valleys, so as to form numerous deep, narrow, steep-walled fiords (Fig. 11). The coast is, in fact, the most ragged of any portion of the border of the continent. All but the higher summits are clothed with a dense mantle of vegetation, the upper limit of which decreases in elevation when followed northward, from about 7,000 feet in the Olympics to approximately 2,500 feet in southern Alaska. Perennial snow exists in the higher valleys and amphitheatres of the Olympics, but the presence of true glaciers in that group of peaks has not been demonstrated. When followed northward the snow-line becomes lower and lower, and well-defined alpine glaciers are known to exist in many of the valleys, more especially on the mainland of British Columbia and southeastern Alaska. There streams of ice descend lower and lower with increase in latitude, and to the north of Stickeen River, in a number of instances, enter the fiords which connect with the ocean and become tide-water glaciers.