M. Kovanko’s General View of the Environs of Pekin. 251 
per bed it passes into a true sandstone, which the quartz 
renders very hard. Occasionally the presence of particles of 
mica give it a slaty texture, and it becomes friable where 
clay is principally the basis of its cement. 
The brook Tsin-Schoui-Khé flows 15 li to the north of 
Van-Pin-Koon, and, in cutting through a mass of diorite, it 
has laid bare all the varieties of this rock. Granitic diorite, 
compact diorite, and porphyritic diorite, alternate with each 
other, all passing at length into a conglomerate, which ap- 
pears to differ from that to which the seams of coal are subor- 
dinate, and is the dioritic conglomerate properly so called. 
The beds of this conglomerate, and those of the diorite itself, 
alternate with beds of ferruginous clay, having a porphyritic 
appearance. This rock in some places passes into euritic 
porphyry, which being sometimes separated, and afterwards 
reunited afresh by the same rock, forms a breccia, in which 
the imbedded fragments of porphyritic rocks are from 1 ver- 
chok up to 3 of an archine in diameter. This porphyry is of 
a brick red colour, with white crystals of felspar ; its hard- 
ness middling, and it forms continuous masses of an irregular 
appearance. 
Carboniferous Limestone.—This limestone shews itself to 
the west of Van-Pin-Koon in considerable masses, which may 
be regarded as an independent formation. The mountains 
which are composed of it have their fianks so steep, that the 
summits are sometimes inaccessible. The texture is foliated 
in thick laminz, and in some localities the stratification of 
the beds is nearly horizontal. It is traversed by veins of per- 
fectly white caleareous spar, which gives to it a variegated 
grey colour. A great many caverns of different dimensions, 
and all of them vaulted, are met with in this limestone; some 
of which contain stalactites, but they are destitute of organic. 
remains. 
The limestone is traversed in the defile of Yan-Li-Gaou by 
veins of galena and brown specular iron-ore, of a quarter of 
an archine or more in thickness. 
Small-grained greyish-yellow sandstone appears in subor- 
dinate beds in this limestone. It is not very hard, contains. 
