general conclusions which appear to result from the facts
observed.
The greater part of Tibet consists ofplutonic and meta-
morphic rocks; and from the gigantic scale on which the sections
are exposed, and the general bareness of the mountains,
which enables their structure to be seen, that country
probably presents the finest field in which these classes
of rocks could be studied. Granite occurs in great abundance,
sending immense veins in all directions into the
metamorphic rocks, which are seen to be everywhere up-
heaved and dislocated by the injected mass. In the
immediate vicinity of the plutonic masses, all traces of
the direction of the strata of the superposed rocks are
lost; but elsewhere, with every variety of dip, it is very
generally found that the stratified rocks strike in a direction
which varies between north-west and south-east, and
north-north-west and south-south-east. As all my observations
were made roughly and unconnectedly, and without
my discovering this identity till after my return to
India, the stnke is probably very uniform throughout a
great extent of country.
It is not a little remarkable that a belt twenty miles
wide, in the direction of this line of strike, drawn from
Iskardo to the Niti pass, would cover every place south
of the Indus in which limestone has been observed in
Tibet. It would pass through Molbil on the Pashkyum
nver, the limestone districts of Zanskar, and the Lacha-
lang pass, where limestone was found by Gerard. It
would also cover Piti, Hangarang, and Bekhar, all well-
known limestone tracts. Of course the limestones of
N-ubra and the Karakoram on the one hand, and of
Kashmir on the other, cannot in any way be connected
with this line.
The sandstones, slates, and conglomerates, which so
closely resemble in appearance those rocks which in
Europe are chiefly members of the old red sandstone
and greywacke series, appear to assume also the same
direction. I bring forward these coincidences of direction
only as a remarkable fact, worthy of investigation,
without attaching any great weight to them, as more careful
observation may show that they are merely accidental,
and that rocks of very different ages exist among the limestones
and associated rocks of the northern Himalaya.
The great extent and development of a very modern
alluvium-like formation, composed of great masses of clay
with boulders, and occasionally of very fine laminated
clay, constitutes one of the most remarkable and striking
features of Western Tibet. In every part through which
I have travelled, and at all elevations, except on the
highest passes, I have found these deposits in greater or
less quantity. In their most common state they consist
of loose earthy or clayey unstratified masses, containing
boulders either angular or rounded. Very fine clay,
distinctly and horizontally stratified, is also common;
sandstone and hardened conglomerate are more rare, but
also occur occasionally.
That some of these beds are of lacustrine origin, the
occurrence of fresh-water shells appears to prove very
clearly; and though here and there small portions may
be terrestrial and of glacial origin, it cannot, I think,
be doubted that the great mass of the boulder clay was
deposited under water.