beautiful and fertile district. The Colorado, draining then as now the western ranges of the Rocky Mountains, spread over the surface of this plateau, enriching and vivifying all parts of it." The cañons of the Colorado have been well described by Professor Powell. The total length of the gorge or chasm is nearly 1000 miles, and it is from 3000 to 6000 feet in depth, cut through the entire series of sedimentary rocks, from the Tertiary to the granite, and even 600 or 800 feet into the latter. "Just in proportion as the Colorado deepened its channel, the region bordering it became more dry, until ultimately the drainage from the mountains passed through it, in what may be termed underground channels, and contributed almost nothing to the moisture of the surrounding country. The reason why the walls of this cañon stand up in such awful precipices of thousands of feet is that the perennial flow of the stream is derived in far distant mountains. Almost no rain falls upon its banks; and when any portion of the bordering cliff has passed beyond the reach of the stream, it stands almost unaffected by atmospheric influences."-(Newberry).

Scattered throughout the Colorado Plateau are several groups of mountains, which rise like islands above the general surface. They are evidently eruptive in their origin, and were comparatively rapid in their growth. They were, however, not volcanic, for the rocks which form them have not spread beyond the centres, where they have lifted dome-like masses of the sedimentary rocks, which frequently are but slightly broken.

Such mountains are the Sierra la Sal, the San Francisco Mountains, the Henry Mountains, the Sierra Abajo, Sierra el Laté, and Sierra Carriso.

4. The Basin Region.

The Great Basin of the West comprises the vast area

that stretches eastward from the Sierra Nevada to the Wahsatch Mountains. It is composed of a multitude of smaller basins or valleys, each of which has its lakes, springs, and watercourses.

This high table-land is a hydrographic basin, whose waters have no visible outlet to the ocean.

Ever since Carboniferous time this region has formed a portion of the continent, although subject to many oscillations.

Scattered over it is a series of remarkable short isolated mountain ranges, separated by valleys whose soil puts desolation in a stronger light. These mountains rise like islands above the desert plains. As Clarence King says, they lie traced across the desert with a north and south trend, and are ordinarily the tops of folds whose deep synclinal valleys are filled with Tertiary and Quaternary detritus.

The northern portion of this central plateau was at times disturbed by the most violent volcanic action from craters, many of which can still be seen. "From these came showers of ashes, which must have covered the land and filled the waters of the lakes so as to destroy immense numbers of the inhabitants of both. These ashes formed strata, which were, in some instances, ten or twenty feet in thickness. At other times the volcanic action was still more intense, and floods of lava were poured out, which formed continuous sheets hundreds of miles in extent, penetrating far into the lake basins, and giving to their bottoms floors of solid basalt. When these cataclysms had passed, quiet was again restored, forests again covered the land, herds dotted its pastures, fishes peopled the waters, and fine sediments, abounding in forms of life, accumulated in new sheets above the strata of cooled lava."-(Newberry).

It is obvious that this Great Basin region was once

occupied by vast fresh-water lakes, which were separated by areas of dry land, on which a luxuriant vegetation flourished, and over which herds of great mammals roamed.

The smaller ranges of mountains were scattered over these lakes as islands, their summits projecting above the surface. The Klamath Lakes, Salt Lake, and Pyramid Lake, are the remnants of these vast bodies. In the northern portion of the basin the drainage effected by the Columbia River was so complete that in many places the sediments which accumulated in the lakes have been cut to a depth of two thousand feet.

In the central portion, however, the waters gradually and slowly passed away by evaporation, and the briny waters have concentrated in the lake basins which have no outlet. Of these Great Salt Lake is a typical specimen. As a salt lake it is of comparatively recent origin. Several times the valley must have been filled high up on the mountain-sides with water-water, too, with very little of the saline character that it now possesses. The complete drainage of the northern and southern portions of the plateau so reduced the water surface of the area, that the moisture in the atmosphere was so much diminished that the dry hot air licked up the water from the undrained lakes, and gradually reduced them to their present dimensions. Although many streams have for ages been pouring a vast volume of water into Salt Lake, the evaporation is so rapid that it is not increased in size, but has gradually diminished. Many of the lakes of the Great Basin are marked only by alkaline plains or "salt flats," while others exist only during a portion of the year, and in the dry season are glittering sheets of salt. Those that remain as lakes are only huge evaporating pans for the drainage from the mountains.

5. The Sierra Nevada, Coast, and Cascade Ranges.

The Sierra Nevada is the loftiest range on the Pacific coast, and in Mount Whitney, which reaches an elevation of 14,898 feet, has the highest mountain peak within the limits of the United States excepting Alaska.

It is also the oldest of the ranges on the Pacific coast. It formed the barrier to the ocean in Jurassic,

Cretaceous, and Tertiary time, although with a much less elevation that it now has.

It is composed mainly " of granitic rocks, associated with which are metamorphic slates proved by the California Survey to be of Triassic and Jurassic age. These slates are traversed in many localities by veins of quartz, which are the repositories of the gold that has made California so famous among the mining districts of the world."

The Sierra Nevada extends from about latitude N. 41°

in Northern California to about N. 36° in the southern part of the State. It is partly volcanic in the northern portion, and its axis is continued northward in the Cascade Range, which is almost entirely volcanic.

The Coast Range is the most modern of the three, and is composed mainly of Cretaceous rocks, with Tertiary occupying the valleys between its numerous sub-ranges. "It forms a raised margin along the western edge of the continent, and has produced that iron-bound coast,' described by all those who have navigated that portion of the Pacific," which washes the shores of the United States.

Between the Coast Range and the Sierra Nevada lies the California Valley, and the same structure reappears in Oregon and in Washington Territory; while, between, the structure is partially obliterated by the encroachment of the mountains.

6. Mineral Resources of the Cordilleras.

The region of the Cordilleras produces nearly all the metals known to commerce, and its mineral resources are as varied as those of any part of the world.

Gold and silver are found in greater or less abundance in nearly every State and Territory in the mountain region and along the coast.

California and Nevada stand at the head of the goldproducing States, the latter also rivalling Mexico in its silver yield. In addition to gold, California yields copper, mercury, tin, iron, salt, and petroleum. Mercury is found at a number of localities in the Coast Range, especially at New Almaden and New Idria, two places named after the two most productive European localities.

The production of these mines, from 1850 to 1868
In 1878 the pro-

inclusive, was nearly 500,000 flasks.