Major Powell has shown how this mighty work of mountain cutting was accomplished; the sawing process was begun, not at the base of the range, but at its top. It is merely a question of age. The Colorado and its chief tributaries are older than the mountain uplifts which they have severed. Moreover, the level of their channels is much the same now as it was before the mountains were born.
The mountain levels, however, have been changing ever since their uplift began. And when the rock layers of which they are composed began to be pushed upward the uplift was so slow that the rivers cut downward just as rapidly. In time the ranges were pushed upward to their present height; but when the uplift was completed, in each case it was sawed to the bottom by the river. It is in very much the same manner that a huge log is cut in twain as it is pushed against the saw. The mountain range, as it is pushed upward, represents the log; the river, which is stationary, represents the saw.
One might look a long way to find the wealth created by this muddy torrent. But the wealth is there, though it is certainly a long way from the canyon; moreover, the rock waste itself is the wealth, and great wealth it is. The water of the river is very muddy. Dip up a bucket filled to the brim and allow it to stand for ten or twelve hours. There is an inch or two of clear water at the top, while at the bottom there is a thick, muddy paste of sand, clay, and red earth. All this rock waste the current is sweeping along to the Gulf of California.
Every overflow along the banks of its lower course spreads this rich, nutritious rock waste over the flood plain. Imperial Valley is filled with it; and this, together with the flood plain above and below, constitutes an area of productive land about as large as the State of Illinois. Moreover, the area is constantly increasing, because of the enormous amount of rock waste which the river daily bears to the Gulf of California. In time, a long time as years are measured, the gulf will be entirely filled—and what a valley of prairie land there will be.
CHAPTER III
YELLOWSTONE PARK
In the northwestern part of Wyoming, at the summit of the continent, is a tract of land containing more than three thousand square miles. It is a region which attracts thousands of sightseers every year; yet inconceivable as it may now seem, this marvellous region was unknown to the world until 1870. Being difficult of access, because flanked by high mountains on all sides, and possessing no mineral deposits of value, there was but little inducement for any one but a hunter or a trapper to penetrate it.
John Coulter, a frontiersman, was probably the first white man to set foot within its territory. He was a member of the Lewis and Clark Expedition and, having observed that there were many beavers in the headwaters of the Missouri River, desired to try trapping there. Having obtained permission to leave the expedition before its return to St. Louis, he forthwith set out to hunt and trap in that region. This was in 1807.