The ice-stream which piled the enormous Bierstadt Moraine took its rise on the west summit slope of Long's Peak. It flowed first toward the west, and in the upper amphitheatre of Glacier Gorge it united with the ice-stream from the north slope of Shoshone Peak and the stream off the eastern slope of Mt. McHenry. Although a part of this enlarged flow appears to have been thrust across the Continental Divide, the larger portion of it was deflected to the north through Glacier Gorge. Emerging from this gorge and enlarged by the ice-streams from Mt. Otis, Mt. Hallett, and other peaks in the Continental Divide, it flowed on to thrust against the eastern base of Flat-Top Mountain. This bent it to the east, and from this turning-point it began to unload its débris on Bierstadt Moraine. A part of its débris was dropped in a smaller parallel moraine on the opposite side of Glacier Creek, and finally a terminal moraine was piled against the western front of Green Mountain, where it almost united with the terminal part of the Moraine on the south side of Moraine Park. The glaciers have formed and distributed much of the soil of this region. Above timber-line there are wide, sedgy meadows and tundras and dry, grassy moorlands. Everywhere on the heights where there is soil there is a growth of Arctic-Alpine vegetation. Above the limits of tree-growth are enormous ragged areas and tiny ledge gardens that are crowded with a variety of brilliantly colored wild blossoms. [Illustration: ESTES PARK ENTRANCE TO THE ROCKY MOUNTAIN NATIONAL PARK] The average altitude of the timber-line is about eleven thousand three hundred feet, nearly a vertical mile higher than the timber-line in the Alps. Timber-line the world over is a place of striking interest, but nowhere have I found or heard of a timber-line which exhibits so many telling features as does the forest-frontier on the eastern side of the Continental Divide. The prevailing tree on the drier slopes at timber-line is _Pinus flexilis_, the limber pine. In the moist places Engelmann spruce predominates, and in many of the moister places there are dwarfed and tangled growths of arctic willow, black birch, and aspen. Among the least broken and most enchanting of the primeval forests of the Park are a few that are grand. One of these is between the head of Fall River and the Poudre; another is in Forest Cañon; one is in the southern part of Wild Basin; still another is on the western slope of Stone's Peak and Flat-Top Mountain. These forests are mostly Engelmann spruce, with a scattering of sub-alpine fir. Around the lower, warmer slopes grows the Western yellow pine, and on the cold lower slopes the Douglas spruce. There are a number of extensive lodge-pole pine forests. These are from thirty to one hundred and thirty years old. Lines of aspen adorn most streams; here and there where the soil is moist they expand into groves.