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CLIMATE AND RAINFALL. 81
mediate solitudes, waterless and destitute of vegetation. But elsewhere the streams
from the Nan-shan and neighbouring highlands are copious enough to flow between
verdant banks northwards to the foot of the advanced spurs of the Tian-shan. The
" deserts " traversed by these rivers are not dismal solitudes like the Takla-makan
of the Tarim basin, or the " Black Sands " and " Red Sands " of the Aralo-Cas-
Water is found almost everywhere near the surface, and springs
pian depression.
bubble up in the hollows, often encircled by extensive oases. Everywhere the
ground is hard and easily traversed by horses and carts. Wayside inns, villages,
and even towns with bazaars and industries have sprung up here and there
along the banks of the running
plantations.
waters in the midst of cultivated lands and
CLIMATE AND RAINFALL.
The cause of this break in the great central desert must be sought in the con-
tours and relief of the continent itself. South of this comparatively fertile belt
the coast-line is deeply indented by the Bay of Bengal, forming a semicircular
curve with a radius of not less than 900 miles. Thanks to this vast marine basin
penetrating far inland between the two peninsulas of India and Indo-China, the
space separating Kansu from the ocean is reduced by one-half. The vapour-charged
clouds are thus borne inland beyond the Kuku-nor district. The atmospheric
currents crossing East Tibet from the Brahmaputra delta to the Mongolian wastes
find no obstacles comparable to those presented farther west by the vast plateau of
Central Tibet, with its plains from 15,000 to 16,000 feet above sea-level, and its
mighty escarpments towering to an altitude of 23,000 or 24,000 feet. The ranges
in the province of Kham are not only less elevated than those of West Tibet, but
also present many breaks of continuity, while often running in parallel lines with
the meridian, thus enabling the southern winds to sweep up the valleys as far as
the Kuku-nor highlands.
The south-west monsoons, which bring such a prodigious quantity of water to
the Brahmaputra basin, are far from being exhausted after crossing the Bayan-
khara range. From April to the end of autumn they bring both snow and rain,
and the atmosphere is really clear and dry only during the winter season. Prje-
Hence it is not
valsky found snow falling daily during the whole month of April.
surprising that sufficient moisture is still discharged beyond the Nan-shan range
to give rise to true rivers, which flow thence far into the plains. Still none of
them are able to reach streams with a seaward outlet, so that all ultimately disap-
pear in saline lakes and marshes overgrown with reeds. The river Ngansi, flow-
ing westwards in the direction of Lob-nor, runs dry in the depression of Khara-
nor, or the "Black Lake." The Az-sind (Ktzina, or Edsinci) receives the waters
of the " Snowy Mountains," after which it is joined north of the Great Wall by
the Tola'i from Suchew. Farther on it gradually diminishes in volume until it
disappears at last in the Sogok-nor and the Sobo-nor on the verge
desert.
of the