Well may the Cañon of the Colorado be called the greatest inanimate wonder in the world. Written in the exposed and remaining rock-strata through which the river has cut its way is a wonderful story of the past, a marvelous and splendid romance. At an enormously remote time the Grand Cañon plateau rose from the primeval sea. After long exposure and great weathering it sank back, remained submerged for ages, and thousands of feet of strata were deposited upon it. Again it emerged, was exposed "a million years and a day," during which æon thousands of feet of strata were eroded away. Again it went down into the sea, and upon it were piled thousands of feet of additional strata. A fourth time it rose slowly above the water. As this plateau was rising, its surface was acted upon by the elements. The part of the plateau surrounding the Grand Cañon proper was the scene of repeated volcanic action and earthquake disturbance. Here the strata have been subjected to repeated faultings, heavings, tiltings, and lava-flows. This uplift imprisoned an enormous Eocene lake that occupied much of what is now the Colorado River basin. This lake the river drained. The drainage was quite probably caused by the fact that the eastern part of the territory was uplifted higher than the western. The drainage-system of the Colorado River, as we now know it, began at that time to take on form and its waters started to cut the cañon. This crude outline covers cycling ages, and probably represents millions of years. Through several thousand years the plateau slowly rose, and all this time the river was gradually cutting its way down into it. Finally the plateau ceased to rise and long remained at a standstill. After cutting down to its first base level, the river had so little fall that its waters, overladen with débris, ceased deepening the channel. The widening of the cañon went steadily on. Again the plateau slowly rose, perhaps two thousand feet. This uplift increased the fall of the river and again set it to deepening its channel, a work it is still doing. The waters of the Colorado River are heavily laden with sediment. During the ages it has transported an inconceivable bulk of eroded material to the ocean. Much of this has come from its three hundred thousand square miles of mountainous drainage basin and all the material which formerly occupied the vast spaces of its numerous cañons. Continual caving of the walls compels the river to spend most of its time and energy in breaking up this débris and carrying it forward to the sea. This condition has existed for thousands of years.