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

CHINA, MONGOLIA, AND JAPAN. 31
hills, occurs in the terrace deposits on their N. W. flank. From this hill we descend
into a small valley which empties into that of the Te Hai. In this valley the terrace
loam is present to the height of probably not less than 250 feet above the lake.
From here the road descends to the deep channel cut through the plateau, which
connects the great valley of the Te Hai with that of the Sankang Ho. This channel
is cut to the bottom of the volcanic mantle, here apparently over 1,000 feet thick,
and into the metamorphic rocks on which it lies.
In this channel we meet with another of those remarkable watersheds of terrace
deposit which stretching from wall to wall, slopes on the west,toward the Te Hai,
and on the east toward the valley of the Sankang Ho. The material forming this
bar is almost loose sand mixed with fragments from the volcanic and metamorphic
rocks, and is but little, if at all, eroded on the western flank, while there are gullies
on the eastern in which highly inclined beds of granulite, containing garnets, are
exposed.
At Maanmiau the valley opens to form the broad, swampy plain of Fungching,
rising from which are frequent low hillocks of gneiss in strata trending between E.
and N. E. Here the high plateau leaves the road; the part that has formed the
southern side of the valley since leaving the Te Hai, now trends away to the S. S. W.
till the steep face and level outline of its edge are lost in the far distance. On the
other side, the part which has formed the northern wall of the valley, continues a
few miles farther, and then, before reaching Fungching, bears away to E. N. E.
Although we have here left the higher plateau, we have not yet reached the southern limit of the volcanic formation. At a level of perhaps 1,000 feet below the
surface of the higher plateau begins the lower plateau, the flat surface of which is
200 or 300 feet above the valley, and extends southward from the very edge of the
higher. It consists of the same volcanic formation as the higher table-land of which
it was, I think, without doubt, once the continuation, the continuity having been
broken by an immense fault-a supposition to which I shall recur further on.
The marshy plain of Fungching is fringed in places with low, flat hills, which owe
their form to the terrace deposit of loam, but under this, consist of a bright red,
sometimes loose material, apparently a wacke or a product of the decomposition of
the volcanic rocks. In this are fragments of a red calcareous mineral, a product
of the action of waters on the adjoining rock before or during its alteration. We
shall see a similar mineral filling crevices in the volcanic plateau formation. It
is perhaps the result of the metamorphic action of mineral springs rising along the
great fault-line.
A few miles beyond Fungching our road rises to the surface of the lower plateau,
and we obtain an open view from a ruined part of the Great Wall. To the north
we can see the precipitous edge of the higher table-land stretching far away to the
northeast, the break in it formed by the valley of the Kir Noor, and its continuation
beyond this toward the Si Ho.1 To the south and east we see the barren crest and
peaks of the Barrier range. Between the higher table-land and this sierra is the
lower plateau on the southernmost spur of which we are standing. The valley we
1 In Mongol, Djookha Gol.