The yellow brownish soil that the tourist sees from Xi'an to Lishan is on the southeast fringe of the loess land. Its extra fineness, sometimes almost like flour, suggests that originally it was wind blown, having been deposited over a large area several million years ago. Its depth ranges from 50 feet to 700 feet. The lower portion could also have been formed by the crushing pressure at the end of the Ice Age. Perhaps a large amount of the original soil was carried away by water and redeposited to the east, where it also took a great length of time to accumulate to its present thickness. This phenomenon affects Chinese history for a number of reasons. Being uniformly fine, this loess soil invited the working of it with primitive tools, such as wooden plows and wooden hoes. The nation-building of the Zhou, teamed with its effort to spread agriculture, apparently was facilitated by this soil property. A consequence was that 1,000 years before the Christian era, China had already attained a degree of cultural homogeneity, the cell structure of her society being aligned with a concomitance of farm production on relatively small plots and kinship cohesion. This is confirmed by contemporary literature, not decisively from any single entry, but with corroborating references from a variety of sources.
Yet the loess was to decide China's fate in a different way. The middle section of the Yellow River, running a north to south course for