because they are so far away. A weary climb of several miles awaits us. We must rest and take breath frequently or we shall not reach the top.

As night approaches and the shadows begin to fall, every turret and pinnacle stands out in bold relief. The bands of yellow and red shade into purple, and everything, save the long winding trail, begins to have a weird and mystical look.

HOW THE COLUMBIA PLATEAU WAS MADE

Years ago people disputed as to the way in which the earth was made. Those who lived where all the rocks had, like lava, the appearance of having once been melted, believed that fire had done all the work. Those who lived where the rocks appeared to be formed of hardened mud, sand, and lime, substances such as we find accumulating under water, said that water alone had been the means. But in later years the earth's surface has been more widely explored, and now it is known that both opinions were partly right. Water and fire have both been concerned in the making of the earth.

In the great valleys fire-formed rocks are rare, but they are more or less abundant in all mountainous regions, for where mountains are, there the crust of the earth is weakest. There are many reasons for believing that the interior of the earth is very hot. We know that the surface is settling in some places and rising in others, and that where the strain of the upheaval is too great the rocks are broken. These convulsions sometimes cause earthquakes and sometimes volcanic eruptions, when enormous quantities of molten rock are poured out over the surface. In all the long history of our earth probably no greater flood of lava than that which made the Columbia plateau was ever spread over the surface of any region. Travel where you will over the plains of southern Idaho, central Washington, or Oregon, and examine the rocks which here and there rise above the soil or are exposed in the cañons, and you will find that they all appear to have been formed by fire.

FIG. 7.—SNAKE RIVER AT IDAHO FALLS

Just beginning to cut a cañon in the volcanic plateau

These rocks are dark in color and very hard. They are not arranged in regular layers like sandstone and shale; many of them show numerous little cavities which once contained steam. These cavities give to the rock a slag-like appearance. In this kind of rock, which we shall call lava, there are, of course, no remains of shells or bones of animals such as are often found in rocks formed from sand or clay.

Do not picture to yourself the Columbia plateau as one continuous stretch of level land, for it is broken by many mountain ranges. Some of these are old mountains which were too tall to be buried by the lava, but most of them have been formed out of the plateau itself. The eruptions which made the plateau extended through a very long time, perhaps hundreds of thousands of years, and the older lava is deeply decayed and covered with soil. Some of the later flows show extremely rough and rugged surfaces and are probably only a few hundred years old.

MAP OF THE COLUMBIA PLATEAU

Long ago, before the eruptions began, the geography of the Northwest was very different from what it is now. Instead of a vast plateau there were mountains and valleys. Lowlands occupied most of the region where the Cascade Range now rises with its lofty volcanic peaks. Portions of the basin of the present Columbia River were occupied by lakes which extended southwest into California.

Movements of the earth began to affect the region of the present plateau, and at many points the solid rocks were fissured and broken. Then from that mysterious region far beneath the surface came steam and gases, escaping through the fissures with explosive force. In some places cinder cones were built about the openings by the fragments of lava which were hurled out. In other places, during periods of less explosive eruption, molten lava flowed out in vast quantities. The lava was very hot and almost as liquid as water, so that it spread in thin sheets over hundreds of square miles of lowland.

One important series of fissures through which eruptions took place marked the line where the Cascade Range was to be built. Other volcanoes appeared over the surface of southern Idaho, central Washington, Oregon, and northeastern California.

The eruptions were not continuous over the whole field; now in this place, now in that, there came long periods of quiet. During such periods the earthquakes ceased, the lava became cold, and the clouds of volcanic ashes cleared from the air. Frequently the lava intercepted streams and blocked the valleys so that large lakes were formed. Whenever the periods of quiet were very long, plants spread over the surface and animals of many kinds made their homes about the lakes.

In eastern Oregon the John Day River and its branches have eroded cañons through the later lava and have exposed the sands, clays, and gravels which collected at the bottom of one of those ancient lakes. In these beds the skeletons of many strange and interesting animals have been found. Evidently they had once lived about the borders of the lake, and the streams had washed their bones into the water and mingled them with the sediment.

FIG. 8.—BLUE LAKES, IDAHO

Formed by springs issuing from underneath the lava of the plateau

One of these animals appears to have been an ancestor of the present horse. It was about the size of a sheep, and had three toes instead of one. Another, probably a very dangerous animal, was related to our present hog, but stood nearly seven feet high. Others resembled the rhinoceros, camel, tapir, or peccary. All but the peccary are now extinct upon this continent. Of the carnivorous animals there were wolves and cats of large size.

The eruptions continued, filling the valleys little by little, until in places the lava reached a thickness of nearly four thousand feet. The lower mountains were hidden from sight. We know of the existence of these buried mountains because the wearing away of the lava in some places has exposed their summits to view.

The lava flood reached farther and farther. In southern Idaho it formed the Snake River plains, which must have been, when first formed, hundreds of miles long, seventy-five miles wide, and almost as even as a floor. If we could have looked on while these things were taking place it would have appeared as if the whole land was about to sink under the fiery mass which flowed out of the earth. The streams and valleys were completely buried. The region of the John Day Lake, with all its animal remains, was covered. The lava, like a sea, crept up against the mountains surrounding the plateau region. Bays of lava extended into the valleys among the mountains, while mountain ridges rose like islands and capes from the surface of the flood.

We never tire of looking at the lofty snow-capped peaks of the Cascade Range. A dozen of them rise over ten thousand feet, and two, Mounts Shasta and Ranier, are more than fourteen thousand feet high. All these mountains were formed of material thrown out of the interior of the earth during the building of the Columbia plateau. The process was very similar for each. About some one exceptionally active crater immense quantities of scoriæ[1] and lapilli[2] accumulated. Then came