entful than that of any other
mountain-range in the world.

Geographically, the Caucasus forms a boundary-line between South-eastern
Europe and Western Asia, but it is not simply a geographical boundary,
marked on the map with a red line and having no other existence: it is a
huge natural barrier seven hundred miles in length and ten thousand feet
in average height, across which, in the course of unnumbered centuries,
man has never been able to find more than two practicable passes, the
Gorge of Dariel and the Iron Gate of Derbend. Beginning at the Straits of
Kertch, opposite the Crimea on the Black Sea, the range trends in a
south-easterly direction across the whole Caucasian isthmus, terminating
on the coast of the Caspian near the half-Russian, half-Persian city of
Baku. Its entire length, measured along the crest of the central ridge,
does not probably exceed seven hundred miles, but for that distance it is
literally one unbroken wall of rock, never falling below eight thousand
feet, and rising in places to heights of sixteen and eighteen thousand,
crowned with glaciers and eternal snow. No other country which I have ever
seen presents in an equally limited area such diversities of climate,
scenery and vegetation as does the isthmus of the Caucasus. On the
northern side of its white jagged backbone lies the barren
wandering-ground of the Nogai Tatars--illimitable steppes, where for
hundreds of miles the weary eye sees in summer only a parched waste of dry
steppe-grass, and in winter an ocean of snow, dotted here and there by the
herds and the black tents of nomadic Mongols. But cross the range from
north to south and the whole face of Nature is changed. From a boundless
steppe you come suddenly into a series of shallow fertile valleys
blossoming with flowers, green with vine-tangled forests, sunny and warm
as the south of France. Sheltered by its rampart of mountains from the
cold northern winds, vegetation here assumes an almost tropical
luxuriance. Prunes, figs, olives and pomegranates grow almost without
cultivation in the open air; the magnificent forests of elm, oak, laurel,
Colchian poplar and walnut are festooned with blossoming vines; and in
autumn the sunny hillsides of Georgia and Mingrelia are fairly purple with
vineyards of ripening grapes. But climate is here only a question of
altitude. Out of these semi-tropical valleys you may climb in a few hours
to the limit of vegetable life, and eat your supper, i