gravel is absolutely bare: in this it contrasts strongly with
similar portions in the valley of the Nubra river, which
are densely wooded. The cause of this difference seems
to lie in the frequent floods which have, at different
periods, devastated the whole course of the Shayuk valley,
from the glaciers of Sassar. These floods, which
appear to be due to the blocking-up of the upper course
of the river by the ice, have been most destructive to the
prosperity of the valley.
Throughout Nubra, the villages, with scarcely an exception,
occupy the surface of the low platforms of alluvium
which fill up the funnel-shaped terminations of the
ravines. In Tibet the size of the villages, and the extent
of cultivation by which they are surrounded, entirely depend
on the supply of water and on the facility with which
it can be diverted from its bed for purposes of irrigation;
and as, in this district, the width and horizontality of the
alluvial tracts are very favourable to the industry of man,
the villages are in general large and surrounded with much
cultivation. Indeed, a super-abundance of water is in
general indicated by the swampy banks of the irrigation
canals, as the water, oozing through the loose gravel of the
platforms, produces a dense jungle of Hippopjhae scrub,
which makes the cultivated tracts conspicuous, even in
winter, when the trees are bare of leaves and the fields of
crops.
This copious supply of water no doubt depends on
the great elevation of the surrounding mountains, which
everywhere rise, if not above, yet almost to the level
of perpetual snow, which is about 18,000 feet, so that
at the head of each little stream there is either a glacier,
or a snow-bed which does not entirely melt till the latter
end of autumn, affording therefore a nearly perennial
supply of water. Even in the hottest months slight
falls of snow are of occasional occurrence at all elevations
above 16,000 feet; and as every range rises much
above that height, a small addition to the supply is thus
obtained.
The villages have generally a few fruit-trees, as well
as a good many poplars and willows, which yield almost
the only timber the inhabitants can command. The
walnut and JElceagnus, both of which trees find their
upper limit in Nubra, are so extremely scarce that they
are not available for such purposes.
In most parts of Nubra the soil is very generally saline,
the dry grassy plains which are common on the banks of
the streams being generally covered with a copious efflorescence
of carbonate of soda; while the abundance of
Salsolce and other Chenopodiaceous plants on the dry
alluvial plains, and even on the rocky hills, seems to
prove that the saline matter is not confined to the immediate
vicinity of water, or to the lowest levels, but is
very generally diffused over the surface.
The valley of the Nubra river, for upwards of twenty
miles, is very similar in general character to that of the
Shayuk. The same wide gravelly expanse occupies its
centre, forming a plain of one or two miles in width,
through which the river runs in many branches. A
great part of this gravelly plain, particularly on the
right side of the valley, is covered by a dense thicket
of Hippophae, extending continuously for four or five
miles, usually impervious, except in certain beaten tracts,
o 2