A few notices of geological formations furnished in the writings of travellers, have already been given in the geographical account of the provinces. The summary published by Davis is a well digested survey of the observations collected by the gentlemen attached to the embassies.[167] ~LOESS-BEDS OF NORTHERN CHINA.~ The loess-beds, covering a great portion of Northern China, are among the most peculiar natural phenomena and interesting fields for geological investigation on the world’s surface. Since attention was first directed to this deposit by Pumpelly, in 1864, its formation and extent have been more carefully examined by other geologists, whose hypotheses are now pretty generally discarded for that of Baron von Richthofen. The loess territory begins, at its eastern limit, with the foot hills of the great alluvial plane. From this rises a terrace of from 90 to 250 feet in height, consisting entirely of loess, and westward of it, in a nearly north and south line, stretches the Tai-hang shan, or dividing range between the alluvial land and the hill country of Shansí. An almost uninterrupted loess-covered country extends west of this line to the Koko-nor and head-waters of the Yellow River. On the north the formation can be traced from the vicinity of Kalgan, along the water-shed of the Mongolian steppes, and into the desert beyond the Ala shan. Toward the south its limits are less sharply defined; though covering all the country of the Wei basin (in Shensí), none is found in Sz’chuen, due south of this valley, but it appears in parts of Honan and Eastern Shantung. Excepting occasional spurs and isolated spots--as at Nanking and the Lakes Poyang and Tungting--loess may be considered as ending everywhere on the north side of the Yangtsz’ valley, and, roughly speaking, to cover the parallelogram between longs. 99° and 115°, and lats. 33° and 41°. The district within China Proper represents a territory half as large again as that of the German Empire, while outside of the Provinces there is reason to believe that loess spreads far toward the east and north. In the Wu-tai shan (Shansí), Richthofen observed this deposit to a height of 7,200 feet above the sea, and supposes that it may occur at higher levels.