Geological researches in China, Mongolia, and Japan, during the years 1862-1865.

40 GEOLOGICAL RESEARCHES IN
is found at the head of the water system of this northern branch of the Yang Ho,
it must be continuous, unless washed away, in all the valleys of this basin between
the plateau and the Barrier range. Thus the deposit in the valley of the Kir
Noor probably continues, through the break in the plateau to the southeast, into the
valley of the Si Ho, and through this to the Yang Ho. Indeed, judging from the
appearance of the region lying between the plateau and the Barrier range, as seen
from the tower at Ha Noor, this deposit seems to occupy here a large area.
We can trace some of the more important islands that were isolated by the lake
in which this deposit originated. One of these seems to have been that part of the
plateau lying between the Si Ho and the Kir Noor. Another instance is the low
ridge that separates the Yang Ho from the Hwaingan creek, while a much larger
one is the hilly country between the Yang Ho and Sankang Ho.
Thus the body of water in which this deposit was formed consisted of a series of
lakes several hundred feet deep, occupying the valleys of the Sankang Ho, Yang
Ho, and Si Ho, and standing at a level sufficiently high to cover the lower watersheds between these streams.
This deposit is everywhere a calcareous loam formed of an almost impalpable
powder, easily crushed between the fingers, and yet so firm that vertical cliffs of it
remain unbroken for many years, which is sufficiently proved by the fact, before
stated, that the inhabitants of the country excavate entire villages in the base of
perpendicular cliffs that rise more than 100 feet above their dwellings. When
breaks occur, the loam falls in immense plates, or tabular masses, leaving a new
vertical face. Near the mountain sides and in the narrow gorges the loam is more
sandy, and contains the gravel and fragments of rocks coming from the immediate
neighborhood, but everywhere else it consists uniformly of an almost impalpable
powder.
A characteristic feature of this loam deposit is its tendency to cleave according
to two vertical planes at right angles to each other, causing it to assume the form of
needles under certain conditions of erosion.
The effects of erosion in this deposit are often very interesting, illustrating in a
marked manner the retrograde formation of ravines. The country is often cut up
by gullies 30 to 70 feet deep, and from 10 to 20 feet wide, with vertical walls. In
these channels wagon roads run for many miles without rising to the plain. In the
valley, between Kwantung (pu) and the Yangkau defile, I crossed a gully 40 or 50
feet deep, and not more than four feet wide, having the same breadth all the way
down, and which, with these dimensions, follows a tortuous course for more than a
mile. In the same valley another ravine of this kind, only eight or nine feet wide,
and not less than 100 feet deep, compelled us to make a detour of over a mile.
Wherever a cliff of this deposit presents itself the beginning of this action is
visible. The surface drainage of a small neighboring area of the plain being concentrated toward one point on the edge of the cliff, cuts, in its fall, a channel from
top to bottom, and this, with each succeeding rain, works its way backward toward
the mountains. As the erosion progresses the sides of the gullies offer new starting
points for tributary ravines.
We have here, in the softest material that can support such action, a repetition