It appears as old as the hills and as fixed and unchanging as they; but, like every frontier, that of the forest is aggressive, is ever struggling to advance. To-day this bold and definite line is the forest's Far North, its farthest reach up the heights; but this simply marks where the forest is, and not where it was or where it is striving to be. Here is the line of battle between the woods and the weather. The elements are insistent with "thus far and no farther," but the trees do not heed, and the relentless elements batter and defy them in a never-ending battle along the timber-line. From a commanding promontory the forest-edge appears like a great shore-line, as it sweeps away for miles along the steep and uneven sides of the mountains. For the most part it follows the contour line; here it goes far out round a peninsula-like headland, there it sweeps away to fold back into cove or cañon and form a forested bay. In Colorado and California this forest-line on the mountains is at an altitude of between eleven and twelve thousand feet. Downward from this line a heavy robe of dark forest drapes the mountains; above it the treeless heights rise cool and apparently barren, piled with old and eroded snowdrifts amid silent moorlands and rocky terraces. The trees of timber-line are stunted by cold, crushed by snow, and distorted by prolonged and terrific winds. Many stretches appear like growths of coarse bushes and uncouth vines. They maintain a perpetual battle, and, though crippled, bent, dwarfed, and deformed, they are stocky and strong old warriors, determined, no weaklings, no cowards. They are crowded together and tangled, presenting a united front. Few trees in this forest-front rise to a greater height than twelve feet. The average height is about eight feet, but the length of some of the prostrate ones is not far from the normal height. Wind and other hard conditions give a few trees the uncouth shapes of prehistoric animals. I measured a vine-like ichthyosaurus that was crawling to leeward, flat upon the earth. It was sixty-seven feet long, and close to the roots its body was thirty-eight inches in diameter. One cone-shaped spruce had a base diameter of four feet and came to a point a few inches less than four feet above the earth. Here and there a tough, tall tree manages to stand erect. The high wind either prevents growing or trims off all limbs that do not point to leeward. Some appear as though molded and pressed into shape. A profile of others, with long, streaming-bannered limbs, gives a hopeful view, for they present an unconquerable and conscious appearance, like tattered pennants or torn, triumphant battle-flags of the victorious forest!