Here again, as in Galicia, we come to a natural frontier, not only between two races, but between two continents. For here, crossing the isthmus between the Black Sea and the Caspian, stretches a mountain range over seven hundred miles in length, rising abruptly out of the plains on either side. These are the Caucasus Mountains, forming the boundary between Europe and Asia.
The higher and central part of the range (which averages only from sixty to seventy miles in width) is formed of parallel ridges, not separated by deep and wide valleys, but remarkably connected by elevated plateaus, which are traversed by narrow fissures of extreme depth. The highest peaks are in the most central chain; Mt. Elburz, attaining an elevation of 18,000 feet above the sea, while Mt. Kasbeck reaches a height of more than 16,000 feet, and several other peaks rise above the line of perpetual snow. The outlying spurs and foothills of this chain of lofty mountains are of less extent and importance than those of almost any other mountain range of similar magnitude, subsiding, as they do, until they are only 200 feet high along the shores of the Black Sea. Some parts are almost entirely bare, but other parts are densely wooded and the secondary ranges near the Black Sea are covered by magnificent forests of oak, beech, ash, maple, and walnut.
This range is an almost impassable wall across the narrow isthmus which joins Europe and Asia, and the Gorge of Dariel is the gateway in this wall through which have come almost all the migrating races that have peopled the continent of Europe. As is well known, the white peoples of Europe have been classified as the Caucasian race, because they were all supposed to have passed through this gateway originally. Apparently each of these oncoming waves of barbaric humanity, bursting through the great gateway, must have left behind some few remnants of their volume, for nowhere in the world, in so limited an area, is there such a diversity and mixture of peoples. In the words of one writer, who speaks with authority on this region, the Caucasus is "an ethnological museum where the invaders of Europe, as they traveled westward to be manufactured into nations, left behind samples of themselves in their raw condition."