grassy for about a mile; its elevation was about 16,500
feet. The pass (Pulokanka La) is a very deep depression
m the axis of the chain, which runs parallel to the left
bank of the Indus, separating the waters tributary to
that river from those which join the Zanskar river, some
of the feeders of the latter springing from the valleys
on the western slopes of these mountains. The hills
right and left of the pass rise very boldly into rugged
masses, contrasting strongly with the level plain which
constitutes the pass, in which the watershed is scarcely
perceptible.
From the pass the descent was considerably more
abrupt than the ascent had been. The valley to the
right was bare and stony, watered by a small streamlet,
which had, as on the eastern face of the pass, cut a deep
channel for itself among boulders. On descending, we
turned gradually to the right, and a lake by degrees came
in view, towards the southern extremity of which the
road advanced over undulating hills of fine clay, full of
fresh-water shells, almost entirely of one species of Lym-
ncea, of which the specimens were extremely numerous.
This lake is the Thogji Chumo of Mr. Trebeck, who
travelled along it on his journey from Le to Piti.
I was much surprised, and not a little pleased, to find
that the clay-beds contained fossils; as, except on one
occasion in Piti, where I found one or two specimens of a
small Planorbis, I had in vain sought in the clayey beds
for any trace of organized beings. Here, however, shells
were in prodigious abundance, and as the species was a
large one, they were very conspicuous. The clay formation
was horizontally stratified, and quite impalpable.
The uppermost beds were at least a hundred feet above
the level of the lake; and as the valley by which we
descended was in its lower part almost horizontal, the
lacustrine beds extended to a considerable distance from
the lake, forming a slightly undulating surface, over
which the road ran.
After reaching the banks of the lake, the road kept
its eastern shore throughout its whole length, which was
about three miles, and we encamped close to its north
end, on the edge of a level salt plain. Our elevation was
about 15,500 feet. The margins of the lake, which was
intensely saline, were generally very shallow, and its banks
often swampy, and covered with saline plants, especially
Chenopodiacece; a species of Suceda, with cylindrical fleshy
leaves, was especially abundant, growing in the soft mud
close to the banks of the lake. A Blysmus, several grasses,
and Ranunculus Cymbalaria were also common along the
banks of the lake. No shells could be seen in the water.
The surrounding hills were not very lofty, but often rose
abruptly several hundred feet, and were in general rugged
and rocky. At the height of perhaps 150 feet
above the lake, a weathered mark could be traced on the
face of the mountains, wherever they were rocky, everywhere
quite horizontal. This was most conspicuous from
a distance, and became indistinct on a near approach. It
appeared to indicate, as I shall hereafter show, the level
of the surface of the lake at some former period.
On the morning of the 25th of September, our day’s
journey commenced by rounding the north end of the
lake, keeping at some distance from its margin to avoid
swamp. For about two miles from the northern end,