^ol. 57.] CHANGES IN NORXHERX AXD CENTRAL ASIA. 245 



our faces were stung by the larger grains of sand which continually 

 dashed against them. On the edge of the Mongolian plateau we 

 frequently saw, and occasionally encountered, vast inverted cones 

 of dust which with a swift whirling movement were travelling over 

 the countr3\ 



The actual agency of wind in the deposition of the loeis is 

 evident throughout the mouutainous tract to the east of the border 

 of the high plateau. AVe crossed over three of these mountain- 

 ridges, each rising 5000 feet above the sea, with intervenins: valleys 

 about 3000 feet lower, and were everywhere struck with the way in 

 which the losss had especially accumulated on the south-east side of 

 the mountains, which was in general the lee side. The resemblance 

 to immense snow-drifts was remarkable. Many villages were 

 built in these huge drifts, the houses being simple excavations, 

 sometimes one storey above another, in this peculiar deposit. 

 Shiwontse, the celebrated Belgian Mission Station, with a popula- 

 tion of 2000, consists almost entirely of houses constructed after 

 this manner. 



Still there were other areas of loess so large and so level 

 that wind would seem incompetent to produce them. These are 

 frequent in the mountain-valleys traversed, but more especially in 

 the extensive plain of loess which extends from the Gulf of Pe 

 Chi Li, 25 miles past Peking, to the Naukau Pass. This plain 

 rises gradually to the west, until, on approaching the mountains, 

 there is much coarse material interstratified with it. Indeed, the 

 mountain-streams are marked by enormous old deltas at their 

 mouths, largely composed of hjess. That in front of the small 

 Nankau Kiver is more than 100 feet above the plain where the 

 stream debouches into it, and is distinctly perceptible for a distance 

 of 5 miles. Pebbles of considerable size were frequent 3 and 

 4 miles from the head of the delta, and its surface sloped at the 

 rate of 100 feet per mile. In the mountainous region the occur- 

 rence of strata of gravel and pebbles in the loess was so frequent as 

 constantly to attract attention. It seems therefore necessary to 

 invoke both wind and water, in order fully to explain the distri- 

 bution of that formation. 



But in any event the deposition of the loess over Eastern China 

 took place at a very recent geological date. Its era is to be 

 reckoned in thousands and tens of thousands of years rather th-m 

 in periods of hundreds of thousands and millions. The period of 

 the loess in China corresponds roup^hly with that of the continental 

 glaciers in Europe and Korth America. This is evident from the 

 rapidity of present erosion, as compared with present subaerial de- 

 position. On approaching the western shore of the Yellow Sea 

 one crosses, 40 miles out, a sharply-cut line on one side of which 

 is clear sea-water, and on the other water turbid with the silt 

 gathered by the rivers from the loess-fields of China. The head 

 of the Gulf of Pe Chi Li has been filled in by sediment from the 

 Peiho for 40 miles since 200 b.c. The land has encroached upon 

 the sea below Tientsin for 18 miles since 500 a.d. Everywhere 



