There are several features in the Puget Sound basin which especially impress the traveller: Next to the magnificence of the lofty volcanic cones that stand like Titan watch-towers along the western slope of the Cascades and the dense forest of gigantic firs and cedars, the most conspicuous feature of the region is the extreme irregularity of the sound itself. Even such general maps of Puget Sound as are usually available indicate that it is exceptional and different from all other water bodies on the continent, not including the extension of the same series of basins northward. Not only is Puget Sound extremely irregular, and inconsistent with any theory that would ascribe its origin to the subsistence and drowning of stream-eroded valleys, but its waters are deep and the channels narrow. The uplands between the waterways are low plateaus composed of clay, gravel, and glacial moraines. The explanation of these unique conditions is that glacial ice formerly occupied the basin and deposited moraines and gravel-plains and clay-plains about its margins; when the branching and irregular sheet of stagnant ice melted its place was taken by the waters of the sea. This simplified outline of the later history of Puget Sound has many modifications, the most important being that there were at least two periods of ice occupation, with an intervening stage of mild climate between, during which the previously formed glacial deposits were forest covered and thick beds of peat formed. [Illustration: FIG. 23.--Puget Sound.] The ice which occupied Puget Sound was the extreme southern portion of a great but irregular Piedmont glacier which fringed the rough and ragged coast of the continent all the way to southern Alaska. A remnant of this former ice body still exists near Mount St. Elias, and constitutes the very instructive Malaspina glacier. THE MOUNTAINS BORDERING THE PACIFIC In a preceding chapter the rugged topography of the western margin of the continent has been briefly described, and a general explanation given of the contrasts which it presents to the coastal plains and plateaus on the Atlantic border. The long, narrow peninsula known as Lower California, as yet unstudied in the light of modern geography, is known to be mountainous throughout. Although nearly surrounded by the waters of the ocean, the climate of the peninsula is hot and arid and its surface desert-like. The Gulf of California, which separates such a large portion of the Pacific border of Mexico from the main body of the republic, has the characteristics of a drowned intermontane or orogenic valley. But whether the great depression was ever dry land or not is unknown. The waters of the gulf are shallow, however, and a moderate upward movement of the earth's crust in that region would transform it into a great valley similar in its general features to the central basin of the State of California.