Geologically speaking, the glaciers were recent. There were several ice invasions, produced probably by the same changes in climate which occasioned the advances of the continental ice sheet east of the Rockies. Matthes describes them as similar to the northern glaciers of the Canadian Rockies of to-day. For unknown thousands of years the Valley was filled by a glacier three or four thousand feet thick, and the surrounding country was covered with tributary ice-fields. Only Cloud's Rest, Half Dome, Sentinel Dome, and the crown of El Capitan emerged above this ice. The glacier greatly widened and considerably deepened the valley, turned its slopes into perpendiculars, and changed its side cascades into waterfalls. When it receded it left Yosemite Valley almost completed. There followed a long period of conditions not unlike those of to-day. Frosts chipped and scaled the granite surfaces, and rains carried away the fragments. The valley bloomed with forests and wild flowers. Then came other glaciers and other intervening periods. The last glacier advanced only to the head of Bridal Veil Meadow. When it melted it left a lake which filled the Valley from wall to wall, three hundred feet deep. Finally the lake filled up with soil, brought down by the streams, and made the floor of the present valley. The centuries since have been a period of decoration and enrichment. Frost and rain have done their perfect work. The incomparable valley is complete. III THE PROPOSED ROOSEVELT NATIONAL PARK INCLUDING THE PRESENT SEQUOIA NATIONAL PARK, WEST CENTRAL CALIFORNIA. AREA, 1,600 SQUARE MILES I Where the lava billows of the Cascade Mountains end in northern California the granite knobs of the Sierra begin. Sharply differentiated in appearance and nature a few miles further in either direction, here their terminals overlap, and so nearly merge that the southern end of the one and the northern beginning of the other are not easily distinguished by the untrained eye. But southward the Sierra Nevada, the snowy saw-toothed range of the Spaniards, the Sierra of modern American phrase, rapidly acquires the bulk and towering height, the craggy cirqued summits and the snowy shoulders which have made it celebrated. Gathering grandeur as it sweeps southward close to the western boundary of California, its western slopes slashed deep with canyons, its granite peaks and domes pushing ever higher above the scattering forests of its middle zones, its eastern ramparts dropping in precipices to the desert, it valiantly guards its sunny state against the passage of eastern highways, and forces hard engineering problems upon the builders of transcontinental railroads. Where it becomes the eastern boundary of the Yosemite National Park it breaks into climaxes of magnificence.