Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/216

122 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DEC. 23, River, a tributary of the former flowing past Kweilin-fu, the capital of Kwangsi province. In the valley of Modo, near Soochow, in Kiangsu, a fine section is also exposed. The Lu-shan, a fine range of mountains near Kiukiang, commanding the entrance to the Poyang lake, is likewise composed of these rocks, which, moreover, appear at intervals through the entire district south of the Yangtse. In the island of Hongkong, and stretching along the sea-coast as far as the Chusan archipelago, they, much altered and associated with igneous rocks of various descriptions, form the main portion of the coast-range. Even in Hongkong itself an attentive examination discovers these slate rocks, but entangled with at least two series of plutonic rocks — one granitic, the other trachytic, and both evidently posterior to the sedimentary rocks. Near Soochow, likewise, in the Modo valley spoken of above, a mass of reddish granite rises from the midst of the lower shales, towards the axis of which the surrounding strata dip.

Fig. 2.- Section of the Kiukiang district, Kiangsu. (Scale 6 miles to 1 inch.)

1 Quartzites. 2. Soft shales and schists.

a. Soft schists, converted into mica-schist and gneiss.

b. Limestone overlain by the Kiukiang laterite, with a base of coarse till containing small boulders.

At the Lu-shan the subsequent origin of the igneous rocks is also well displayed in the conversion of a portion of the superincumbent shales into mica-schist and gneiss ; in Lower Kiangsu, likewise, the detached hills which appear over the surface of the alluvial plain are composed of the remains of these quartzites preserved from the denudation which destroyed the other portions of the series by the hardening effect of the intrusion of a series of porphyritic dykes having a general direction from W.S.W. to E.N.E.

Lying, as above stated, conformably over the Tungting grits, is a great mass of limestone, containing near its base, in the central provinces at least, a mass of shales of no great thickness producing coal and iron. Throughout the valley of the Yangtse, from the Taihu in Kiangsu westwards to the province of Hupeh, I have traced the lower bed, No. 4, of the series. This bed where exposed is rendered very conspicuous from projecting nodules of black chert jutting out far beyond the water-worn and often honeycombed limestone matrix ; in fact one of the chief features of the series in the provinces of Kwangtung and Kwangsi is the extraordinary extent to which the solvent power of water has acted on the rock. In the valley of the