Captain Gerard distinguishes between the summits that rise in the
middle of the plateau, where he states the elevation of the snow-line to be
between 18,000 and 19,000 feet, and the northern slopes of the chain of the
Himalaya, which border on the defile of the Sutledge, and can radiate but
little heat, owing to the deep ravines with which they are intersected. The
elevation of the village of Tangno is given at only 9300 feet, while that of
the plateau surrounding the sacred lake of Maqasa is 17,000 feet. Captain
Gerard finds the snow-line 500 feet lower on the northern slopes, where the
chain of the Himalaya is broken through, than toward the southern
declivities facing Hindostan, and he there estimates the line of perpetual
snow at 15,000 feet. The most striking differences are presented between
the vegetation on the Thibetian plateau and that characteristic of the
southern slopes of the Himalaya. On the latter the cultivation of grain is
arrested at 9974 feet and even there the corn has often to be cut when the
blades are still green. The extreme limit of forests of tall oaks and
deodars is 11,960 feet; that of dwarf birches, 12,983 feet. On the plains,
Captain Gerard found pastures up to the height of 17,000 feet; the cereals
will grow at 14,100 feet, or even at 18,540 feet; birches with tall stems at
14,100 feet, and copse or brush wood applicable for fuel is found at an
elevation of upward of 17,000 feet, that is to say, 1280 feet and above the
lower limits of the snow-line at the equator, in the province of Quito.
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