This is one of the reasons for the extraordinary distinction of the reservation appropriately called the Rocky Mountain National Park, namely that it is the only true example of the continental mountain system in the catalogue of our national parks. It is well, therefore, to lay the foundations for a sound comprehension of its differentiating features. The Rocky Mountains, which began to rise at the close of the Cretaceous Period at a rate so slow that geologists think they are making a pace to-day as rapid as their maximum, extend from the plateau of New Mexico northwesterly until they merge into the mountains of eastern Alaska. In the United States physiographers consider them in two groups, the Northern Rockies and the Southern Rockies, the point of division being the elevated Wyoming Basin. There are numerous ranges, known, like the Wasatch Mountains, by different names, which nevertheless are consistent parts of the Rocky Mountain System. The Rockies attain their most imposing mass and magnificence in their southern group, culminating in Colorado. So stupendous is this heaping together of granitic masses that in Colorado alone are found forty-two of the fifty-five named peaks in the United States which attain the altitude of fourteen thousand feet. Of the others, twelve are in the Sierra of California, and one, Mount Rainier, in Washington. Mount Elbert, in Colorado, our second highest peak, rises within eighty-two feet of the height of California's Mount Whitney, our first in rank; Colorado's Mount Massive attains an altitude only four feet less than Washington's Mount Rainier, which ranks third. In point of mass, one seventh of Colorado rises above ten thousand feet of altitude. The state contains three hundred and fifty peaks above eleven thousand feet of altitude, two hundred and twenty peaks above twelve thousand feet, and a hundred and fifty peaks above thirteen thousand feet; besides the forty-two named peaks which exceed fourteen thousand feet, there are at least three others which are unnamed. Geologists call the Rockies young, by which they mean anything, say, from five to twenty million years. They are more or less contemporary with the Sierra. Like the Sierra, the mountains we see to-day are not the first; several times their ranges have uplifted upon wrecks of former ranges, which had yielded to the assaults of frost and rain. Before they first appeared, parts of the Eastern Appalachians had paralleled our eastern sea coast for many million years. The Age of Mammals had well dawned before they became a feature in a landscape which previously had been a mid-continental sea. II