south-west and north-east respectively, follow longitudinal valleys, and
the Aar and the Ticino, flowing north-west and south-east respectively,
follow transverse valleys, in the Caucasus the streams which flow
south-west and north-east, namely, the headwaters of the Rion and the
Terek, travel along transverse valleys, and those of the Kura and the
Kuban, flowing south-east and north-west respectively, traverse
longitudinal valleys. For purposes of description it is convenient to
consider the range in four sections, a western, a middle with two
subsections, and an eastern.

1. WESTERN CAUCASUS. This section, extending from the Strait of Kerch to
Mount Elbruz in 42 deg. 40' E., is over 420 m. long, and runs parallel
to the north-east coast of the Black Sea and at only a short distance
from it. Between the main range and the sea there intervene at least two
parallel ranges separated by deep glens, and behind it a third
subsidiary parallel range, likewise separated by a deep trough-like
valley, and known as the Bokovoi Khrebet. All these ranges are shorn
through transversely by numerous glens and gorges, and, the rainfall
being heavy and the exposure favourable, they are densely clothed with
vegetation. Many of the spurs or broken segments of ranges thus formed
abut steeply upon the Black Sea, so that this littoral region is on the
whole very rugged and not readily accessible, especially as the general
elevations are considerable. The seaward flanking ranges run up to 4000
ft. and more, and in many places shoot out cliffs which overhang the
coast some 2000-3000 ft. sheer, while the main range gradually ascends
to 10,000-12,000 ft. as it advances eastwards, the principal peaks being
Fisht (8040 ft.), Oshten (9210 ft.), Shuguz (10,640 ft.), and Psysh
(12,425 ft.). And whereas the main range is built up of hard eruptive or
crystalline rocks, the subsidiary chains are composed of softer
(Cretaceous and Tertiary) laminated formations, which easily become
disintegrated and dislocated. The snow-line runs here at about 9000 ft.
on the loftiest summits, and east of Oshten the crest of the main range
is capped with perpetual snow and carries many hanging glaciers, while
larger glaciers creep down the principal valleys. The passes lie at
relatively great altitudes and are few in number, so that although the
northern versants of the various ranges all have a tolerably gentle
slope, communication between the Black Sea and the valley o