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

12 GEOLOGICAL RESEARCHES IN
The porphyry conglomerates, No. 2, which, in places along the northern edge of
the basin, have a thickness of not less than 2000 feet, are wanting in the eastern
part. The parts of the series marked No. 3, form the oldest beds, and they
rest immediately on the limestone in their respective localities. Between Nos. 3
and 4 the character and extent of the intervening beds were not observed. The
connection between Nos. 4 and 5 is made on lithological grounds, the same green
sandstone and green quartzose conglomerate occurring above the coal seams of
Muntakau, and low down in the series at Chaitang.
Limestone.-Here, as on the Yangtse, a great development of limestone forms
the floor of the Coal measures. Although no good opportunity occurred, in this
region, for estimating its thickness, this is undoubtedly several thousand feet. It
is generally divided into two nearly equal parts by a bed of clay slates; though
independently of this, the upper and lower strata are characterized, the latter by
an abundance of chert, and the former by comparative freedom from that mineral.
The limestone is generally compact and blue, but in places it is white and saccharoid; and black, pink, and dark red varieties occur. The chert is black, and
is abundant in the lower half, occurring in nodules, and in layers varying in thickness from less than one line to over forty feet, beds of this size generally forming
the bottom of the limestone. In the basin of Siuenhwa (fu), near the Great
Wall, the limestone is highly siliceous, but almost always retains a white appearance.
This formation furnishes, here, as in almost every province of the empire, besides
lime, the marble so much used in Chinese ornamental architecture, for bridges,
tombstones, gateways, and the lions that guard the portals of all official buildings.
The white saccharoid variety is very beautiful, but disintegrates so rapidly that,
even in the dry climate of Peking, inscriptions on exposed monuments two hundred
years old are barely legible.' The black variety, which is very compact, breaking
with a conchoidal fracture, retains a perfectly fresh surface after centuries of
exposure.
A quarry at the Maanshan has supplied lime for the capital during many centuries; the continued excavation having widened and deepened the valley, removing
small hills and leaving, over an area of perhaps one square mile, a deposit that
might well perplex an observer, were the cause not still at work. Almost every
point in this area seems to have been the site of a lime-kiln, which has left its
cone of concentric layers, consisting of half burnt limestone, chert, fragments of
coal and ashes. As new kilns were built over and between old ones, the result is
a bed, the ingredients of -which have become cemented to a hard concrete, by the
refuse lime. In this deposit, the stream of the valley has cut its channel, in places,
forty to fifty feet deep, with vertical walls, without reaching the limestone bottom.
Caves are abundant in this limestone, and many of them are said to be of great
extent. One which I visited, near Fangshan (hien), consists of a series of large' There is a white variety, used in monuments near Peking, in which inscriptions of the Kin
dynasty are perfectly fresh, as, for instance, that used in the grand marble arch of Kiyungkwan in
the Nankau pass.