Terrain. China Proper is an immense mountainous area bounded by the Pacific Ocean to the east and south, the massive Himalaya and Pamir mountain ranges to the west and southwest, and the steppes to the north. Although the North China Plain is large, it is actually much smaller than the plain that extends across northern India, the North European Plain, or the American Middle West. The Qinling mountain range divides China into two drainage systems: the Yellow River in the North and the Yangzi (Yangtze) River in the South.

Loess. The winds blowing outward from the continent are cold and dry. These winds, producing vast dust storms, deposited in ancient times the fine loess soil that now covers about one hundred thousand square miles of northwestern China south of the Great Wall. The loess is from one hundred feet to three hundred feet thick. The Yellow River spread...