tation when present is scanty, and only such as is characteristic of a dry and almost desert country.

Nearly every stream flows in a cañon, a narrow valley, with precipitous walls. The cañons of this region are all quite similar in their cross-sections. The upper edge is very sharply cut. At the top is a cliff, vertical, or nearly so, of a proportional height varying extremely. At the foot of this is a steep slope of talus. The more rapid the stream the narrower is the cañon, and the less the amount of debris; so that, in the case of some of the swiftest torrents, the cañons consist simply of two vertical walls, closely enclosing the stream-bed In the case of large streams, we frequently find a modification of this form. The cañon wall presents a series of benches from top to bottom, as though a series of cañons had been cut, one within another. At the foot of each bench there is, in nearly or quite all cases, a change in the character of the rock, that of the lower portion being the harder. Many beautiful examples of this kind of cañon have been observed by the writer.

Most of the cañons are cut in stratified rocks, nearly or quite horizontally bedded. Horizontal sections of these cañons show long, smooth curves, with no sharp angles. Vertical sections show abrupt precipices, and narrow benches, with sharp angles. Cañons cut in granite and trachyte, on the other hand, show very rugged horizontal, as well as vertical, sections. They have little or no talus, and very narrow bottoms. They are merely rugged notches.

These two classes of rocks are frequently combined in one cañon, forming a double cañon. This is the case with the Grand Cañon of the Gunnison, and in a portion of the Grand Cañon of the Colorado In the former, in the lower part of the cañon, about two thousand feet in height, the walls are extremely precipitous and rugged, and the river fills the bottom completely, leaving no beach whatever. At the top of the gneiss is a bench, nearly horizontal, extending back a few hundred feet, whence rises steeply a slope of talus, capped by a precipice of about two hundred feet. The whole height of the upper cañon is about one thousand feet.

The cutting of cañons of the general class described above, is confined almost entirely to Colorado drainage. With the excep tion of the cañon of the Snake river, in the basalt plateau of Idaho, the cañons of erosion are simple gorges by which streams traverse mountain ranges.

Now, why does this condition exist? Why is it that on this slope every stream cuts a cañon, while on the eastern slope, on the great plains, there are no cañons whatever? This is due to several causes, all which may be traced directly to the aridity of the climate and the amount and character of the rainfall. The atmosphere is extremely dry; the rainfall is very slight, and the little that falls comes, not in long storms, but in sudden deluges. From the dryness of the atmosphere and the want of moisture of the surface, there is little vegetation-very little indeed of arborescent vegetation; and, both as a cause and result, little or no soil. The rains, coming as they always do in floods, run immediately off the bare rock, or over and through the thin sandy soil, sweeping it with them, and collecting in the little runs with incredible rapidity, rush down them in great body and with great velocity, sweeping everything before them. The waters are turbid and thick with sediment, coarse and sharp-edged from the rapid cutting of the rocks. This sand and gravel carried in suspension is the principal cutting agent, as water alone has but little cutting power. The high winds also, which are very frequent in this country, fulfil their part, and a very important one in this work, in planing off the surface, and leaving their shavings in the form of sand for the waters to take up. The erosive power of these high winds, with the sand which they set in motion, is very great. A well-known example of their power is seen in the chiseling of the monuments in Monument Park, near Colorado Springs, Colorado. Numberless similar examples may be seen in the country of the Colorado River.

The difference between the conditions here and in other parts of the West is mainly one of degree only; but the results are widely different. In the case of the plains, on the eastern slope, the climate is moister, the rainfall greater, and the storms are of greater duration, and of a less sudden and explosive character. As will be seen farther on, the slopes of the streams are as great or even greater, showing that this element does not produce any of the effect in question. In consequence of this difference in meteorological conditions, the materials for soil, instead of being washed immediately into the water courses, and thence carried on by the streams as cutting agents, collect and become covered with vegetation. This, in turn, in great measure, prevents sudden floods.

The existence of this great plateau region was scarcely suspected

before the time of the Pacific Railroad explorations, which commenced about 1853. Captain Gunnison, with one of the parties engaged in this work, traveled down the Gunnison, and the Grand nearly to its mouth, and crossed the Green, traversing the whole width of this area without, so far as indicated by his report, suspecting that he was in a peculiar country. He was engaged in the discharge of his duty, which was to discover a practicable route for a railroad, and had no energies to spare for ulterior aims; although the geologist of his expedition might have been expected to see what lay before his eyes.

The party in charge of Lieut. Whipple, whose route was on or near the 35th parallel of latitude, crossed the plateau near the head of the Colorado Chiquito, and the geological report, written by Prof. W. P. Blake from the notes of Mr. Marcou, who accompanied the expedition as geologist, recognizes the character of the country which was traversed. In 1857-58 Lieut. Ives, acting under the War Department, went up the' Colorado in a small steamer to the foot of the Black Cañon, about 500 miles above its mouth, and made an elaborate reconnoissance. Leaving the river near this point, he crossed the plateau in an easterly direction to Fort Defiance, New Mexico. On his way, he succeeded in reaching the edge of the Grand Cañon in two places, at the mouths of Diamond creek and of the Colorado Chiquito. The geological report of this expedition, written by Dr. Newberry, who accompanied it, first recognized the existence of this vast system of plateaus and cañons. It has remained for later explorations and surveys to develop our knowledge of the country in anything like detail.

With regard to the immediate course of the Colorado above the head of steamboat navigation, very little was known until quite recently. It was known that the river ran for a part, at least of its course-t —through a tremendous cañon, in the great table-lands of which the country was made up; a cañon so deep that, in Western parlance, it required "the combined efforts of several men to see to the bottom." Wild stories of the river's having cut tunnels for itself in places were current, and stories of fabulously great falls obtained full credence. The two views of the Grand Cañon which Lieut. Ives had obtained, served but to give basis to these extravaganzas. The stories told by trappers and prospectors, who had,

in their wanderings, reached the margin of the cañon, were worthy of the Arabian Nights.

The first information which was at all authentic, concerning the river's course and its cañon, above the point which Ives reached, is contained in a paper by Dr. C. C. Parry, read before the Academy of Natural Sciences of St. Louis. It consists of an account of the descent of the cañon of the Colorado, by one James White, in 1867. The account states that he, with two companions, had been on a prospecting trip in the San Juan mountains, in southwestern Colorado. Not having much success, they turned their backs on the mountain, and traveled down the Mancos and San Juan rivers. They followed the latter stream down to the head of its cañon, where they left it and went northward to the Grand River, crossing on their way a range of mountains. They reached the Grand about eighteen miles above its mouth, and, looking for a place to descend from the plateau, followed it up for twelve miles, when they found a way down and crossed the river; but in climbing to the summit of the plateau on the other side, were attacked by Indians, and one of their number killed. The two remaining made their way back to the river, hastily constructed a raft, and started down the stream. Soon after passing the mouth of the San Juan, on the fourth day of their adventurous voyage, White's companion was washed off the raft and drowned. All the provisions were lost at the same time, and thenceforward White suffered much from hunger. On the fourteenth day, he reached Callville, at the mouth of the Virgen, more nearly dead than alive.

The facts which White observed in this terrible trip have been confirmed by Major Powell's observations, and show his account to be authentic; for instance, that the junction of the San Juan is in a heavy cañon, and that there are no large cataracts or any perpendicular falls. The average height of the cañon walls White estimated at 3000 feet, which is not far from the truth respecting the immediate cañon. The upper benches, which, though set back some distance from the edge, can properly be regarded as part of the cañon, could not have been seen by him, drifting along at the bottom of the abyss. He speaks of passing for days between walls of darkcolored, igneous rock, which is undoubtedly the granite that Major Powell notes in the Grand Cañon.

In 1869 an attempt was made to navigate the Grand river by

Capt. Samuel Adams. He started at Breckinridge, Colorado, near the head of the Blue, and succeeded in getting to the mouth of the Blue and down the Grand a short distance, when his boats were wrecked and the expedition was abandoned.

At this time enough was known concerning the character of the country bordering the Colorado and Green rivers to show that the only practicable way of exploring these streams would be by following them down in boats. The impassable character of the crosscañons alone made it impossible to follow the streams by land, even without the additional difficulty from want of water and vegetation. Acting on the above conclusion, Major J. W. Powell undertook to navigate the rivers through the whole length of the cañon country, from Green River station, on the Union Pacific Railroad, to Callville, at the mouth of the Rio Virgen. The story of this trip has been told most admirably by Major Powell himself, in the pages of Scribner's Magazine, and also in his report, made to the Secretary of the Smithsonian Institution; so that it will be necessary here to make merely the briefest recapitulation of the events, and a short sketch of the results of this adventurous voyage.

He started late in May, 1869, with a party of ten men, in four boats. They met with various adventures incident to such a voyage on a swift stream, but no serious mishaps, and on August 30th arrived safely at the mouth of the Rio Virgen. They found no falls and no very bad rapids: in many places were obliged to make portages, some of them long and difficult. They were forced to run several rapids; and one can easily imagine that, at times, the traveling was exciting enough.

The branches of the Colorado and the Green from the East, the the Tampa, the White, the Grand and the San Juan, have been examined from their heads nearly or quite to their mouths by the survey under the charge of Dr. F. V. Hayden.

Starting at the head of the Green River, we find it traversing in a southerly direction a desert country, of alkaline soil, producing a rank growth of that staple product of the West, artemisia, or, popularly, sage-brush. This is the Green River basin. At the foot of this basin the river meets the Uinta range, trending east and west, directly across its course. This range it traverses, by a devious course, cutting gorges of enormous depth, and on its way receives the waters of the Tampa. On emerging from the mountains it enters