years at most out of all infinity, which ever can greatly concern man, for during this time were laid the only rocks whose reading was assisted by the presence of fossils. During this time the continents attained their final shape, the mountains rose, and valleys, plains, and rivers formed and re-formed many times before assuming the passing forms which they now show. During this time also life evolved from its inferred beginnings in the late Archean to the complicated, finely developed, and in man's case highly mentalized and spiritualized organization of To-day.

Surely the geologist's field of labor is replete with interest, inspiration, even romance. But because it has become so saturated with technicality as to become almost a popular bugaboo, let us attempt no special study, but rather cull from its voluminous records those simple facts and perspectives which will reveal to us this greatest of all story books, our old earth, as the volume of enchantment that it really is.

With the passing of the Archean, the earth had not yet settled into the perfectly balanced sphere which Nature destined it to be. In some places the rock was more compactly squeezed than in others, and these denser masses eventually were forced violently into neighbor masses which were not so tightly squeezed. These movements far below the surface shifted the surface balance and became one of many complicated and little known causes impelling the crust here to slowly rise and there to slowly fall. Thus in places sea bottoms lifted above the surface and became land, while lands elsewhere settled and became seas. There are areas which have alternated many times between land and sea; this is why we find limestones which were formed in the sea overlying shales which were formed in fresh water, which in turn overlie sandstones which once were beaches—all these now in plateaus thousands of feet above the ocean's level.

Sometimes these mysterious internal forces lifted the surface in long waves. Thus mountain chains and mountain systems were created. Often their summits, worn down by frosts and rains, disclose the core of rock which, ages before, then hot and fluid, had underlain the crust and bent it upward into mountain form. Now, cold and hard, these masses are disclosed as the granite of to-day's landscape, or as other igneous rocks of earth's interior which now cover broad surface areas, mingled with the stratified or water-made rocks which the surface only produces. But this has not always been the fate of the under-surface molten rocks, for sometimes they have burst by volcanic vents clear through the crust of earth, where, turned instantly to pumice and lava by release from pressure, they build great surface cones, cover broad plains and fill basins and valleys.

Thus were created the three great divisions of the rocks which form the three great divisions of scenery, the sediments, the granites, and the lavas.

During these changes in the levels of enormous surface areas, the frosts and water have been industriously working down the elevations of the land. Nature forever seeks a level. The snows of winter, melting at midday, sink into the rocks' minutest cracks. Expanded by the frosts, the imprisoned water pries open and chips the surface. The rains of spring and summer wash the chippings and other débris into rivulets, which carry them into mountain torrents, which rush them into rivers, which sweep them into oceans, which deposit them for the upbuilding of the bottoms. Always the level! Thousands of square miles of California were built up from ocean's bottom with sediments chiselled from the mountains of Wyoming, Colorado, and Utah, and swept seaward through the Grand Canyon.

These mills grind without rest or pause. The atmosphere gathers the moisture from the sea, the winds roll it in clouds to the land, the mountains catch and chill the clouds, and the resulting rains hurry back to the sea in rivers bearing heavy freights of soil. Spring, summer, autumn, winter, day and night, the mills of Nature labor unceasingly to produce her level. If ever this earth is really finished to Nature's liking, it will be as round and polished as a billiard ball.