The weight of this superimposed icy stratum was immense; it was greater than the bottom layers could support. Ice is plastic--rubbery--if sufficient pressure or weight be applied. Under the enormous pressure the bottom layers started to crawl or flow from beneath like squeezed dough. This forced mass moved outward and downward in the direction of the least resistance,--down the slope. Thus a glacier is conceived and born. Numbers of these glaciers--immense serpents and tongues of ice--extended down the slopes, in places miles beyond the line of perpetual snow. Some of these were miles in length, a thousand or more feet wide, and hundreds of feet deep, and they forced and crushed their way irresistibly. It is probable they had a sustained, continuous flow for centuries. A glacier is one of the natural wonders of the world and well might every one pay a visit to one of these great earth-sculpturers. The time to visit a glacier is during late summer, when the snows of the preceding winter are most completely removed from the surface. With the snows removed, the beauty of the ice and its almost stratified make-up are revealed. The snow, too, conceals the yawning _bergschlunds_ and the dangerous, splendid crevasses. A visit to one of these ponderous, patient, and effective monsters is not without danger; concealed crevasses, or thinly covered icy caverns, or recently deposited and insecurely placed boulders on the moraines are potent dangers that require vigilance to avoid. However, the careful explorer will find one of these places far safer than the city's chaotic and crowded street. [Illustration: A CREVASSE] For the study of old glacier records few places can equal the Estes Park district in Colorado. The Arapahoe, on Arapahoe Peak, Colorado, is an excellent glacier to visit. It is characteristic and is easy of access. It is close to civilization,--within a few miles of a railroad,--is comprehensively situated, and is amid some of the grandest scenery in the Rocky Mountains. It has been mapped and studied, and its rate of movement and many other things concerning it are accurately known. It is the abstract and brief chronicle of the Ice Age, a key to all the glacier ways and secrets. In the Arapahoe Glacier one may see the cirque in which the snow is deposited or drifted by the wind; and the bergschlund-yawn--crack of separation--made by glacier ice where it moves away from the névé or snowy ice above. In walking over the ice in summer one may see or descend into the crevasses. These deep, wide cracks, miniature cañons, are caused by the ice flowing over inequalities in the surface. At the end of this glacier one may see the terminal moraine,--a raw, muddy pile of powdered, crushed, and rounded rocks. Farther along down the slope one may see the lakes that were made, the rocks that were polished, and the lateral moraine deposited by the glacier in its bigger days,--times when the Ice King almost conquered the earth.