The highest timber-line in the world is probably on Mount Orizaba, Mexico. Frank M. Chapman says that there are short-leaved pines (_Pinus Montezumæ_) from thirty to forty feet high, on the southern exposure of this peak at an altitude of about 13,800 feet. In Switzerland, along the steep and snowy Alps, it is sixty-four hundred; on Mt. Washington, about forty-five hundred feet. In the mountains of Colorado and California it is of approximately equal altitude, between eleven and twelve thousand feet. Advancing northward from California along the timber-line, one enters regions of heavy snow-fall as well as of restricting latitude. Combined, these speedily lower the altitude of timber-line, until on Mt. Rainier it is below eight thousand feet. There is a noticeable dwarfing of the forest as one approaches the Land of the Midnight Sun, and in its more northerly reaches it comes down to sea-level to form the Land of Little Sticks. It frays out at its Farthest North just within the Arctic Circle. Most of the Arctic Ocean's icy waves break on treeless shores. Everywhere at timber-line the temperature is low, and on Long's Peak the daily average is two degrees below the freezing-point. At timber-line snow may fall any day of the year, and wintry conditions annually prevail from nine to ten months. The hardy trees which maintain this line have adjusted themselves to the extremely short growing-season, and now and then mature and scatter fertile seeds. The trees that do heroic service on all latitudinal and altitudinal timber-lines of the earth are members of the pine, spruce, fir, birch, willow, and aspen families. At timber-line on the Rocky Mountains there are three members each from the deciduous trees and the evergreens. These are the Engelmann spruce, limber pine, alpine fir, arctic willow, black birch, and quaking aspen. A few timber-line trees live a thousand years, but half this time is a ripe old age for most timber-line veterans. The age of these trees cannot be judged by their size, nor by general appearance. There may be centuries of difference in the ages of two arm-in-arm trees of similar size. I examined two trees that were growing within a few yards of each other in the shelter of a crag. One was fourteen feet high and sixteen inches in diameter, and had three hundred and thirty-seven annual rings. The other was seven feet high and five inches in diameter, and had lived four hundred and ninety-two years!