THE GEOLOGIC HISTORY OF CHINA 117 



The thousands of junks which ply these waterways maintain a volume 

 of inland commerce, which is inferior only to that of the great railroad 

 countries, such as the United States. The relative freedom of com- 

 munication in this great plain of the Yellow Eiver has helped to bring 

 about a greater homogeneity in the people than in any other equally 

 large part of China. Here we find a single dialect in use over the en- 

 tire region, whereas in some parts of southern China the natives of 

 even adjacent valleys speak languages almost unintelligible to each 

 other. The other common effects of isolation, such as the lack of ac- 

 quaintance with the customs of outside peoples, the hatred of foreign- 

 ers, the peculiar local usages, and many other things, are less promi- 

 nent here than in other parts of the empire. Excepting the coastal 

 cities, there is no safer part of China for foreigners to travel through. 



West and northwest of the Yellow Eiver plain lie the more rugged 

 plateaus and mountains of northwest China, with their sub-arid climate 

 presaging the approach to the deserts of Mongolia. Over much of this 

 region the ancient limestones and sandstones are still horizontal or 

 are gently folded, with occasional dislocations along faults. On ac- 

 count of the comparatively recent uplift and differential warping which 

 this part of China has suffered, the streams have been greatly accel- 

 erated in their work, so that they have hollowed out canyons in the 

 raised portions and have filled in the depressed basins with sand and 

 silt. This is the region celebrated among geologists on account of the 

 loess, or yellow earth, which lines the basins and mantles the hillsides 

 everywhere. It is believed that this is very largely a deposit of wind- 

 blown dust, although it has been worked over considerably by the 

 streams from time to time. No doubt Baron von Eichthofen, the dis- 

 tinguished German explorer, was near the truth when he concluded 

 more than forty years ago, that the " yellow earth " was the dust of the 

 central Asian deserts carried into China by the northwest winds. The 

 presence of the loess determines, in large measure, the mode of living 

 adopted by the inhabitants. Because of its fertility and moisture-con- 

 serving properties, it is well adapted to dry farming, and there is little 

 water for irrigation. The Chinese are not content with using the level 

 bottom lands, but successfully cultivate the hillsides wherever a de- 

 posit of the loess remains. In order to prevent the soil from washing 

 off from these steep slopes, they build a series of stone walls, thus form- 

 ing soil reservoirs or terraces. In this way nearly all of the soil is 

 utilized. 



In such a country rivers are not numerous and those which exist 

 have many rapids and shoals. Boats are therefore but little used in 

 northwest China. For both passenger and freight traffic, pack animals 

 or rude vehicles are the chief reliance. For passengers there are also 

 the palanquin or sedan-chair and the mule-litter. Where the country 

 is not too rough, the two-wheeled cart is the usual conveyance for mer- 



