Sz’chuen is naturally divided by the four great rivers which run from north to south into the Yangtsz’, and thus form parallel basins; as a whole these comprise about half of the entire area, and all of the valuable portion. The western part beyond the Min River belongs to the high table lands of Central Asia, and is little else than a series of mountain ranges, sparsely populated and unfit for cultivation, except in small spaces and bottom lands. The eastern portion is a triangular shaped region surrounded with high mountains composed of Silurian and Devonian formations with intervening deposits, mostly of red clayey sandstone, imparting a peculiar brick color, which has led Baron von Richthofen to call it the Red Basin. The ranges of hills average about 3,500 feet high, but the rivers have cut their channels through the deposits from 1,500 to 2,500 feet deep, making the travel up and down their waters neither rapid nor easy. The towns which define this triangular red basin are Kweichau on the Yangtsz’, from which a line running south of the river to Pingshan hien, not far from Süchau at its confluence with the Min, gives the southern border; thence taking a circuit as far west as Yachau fu on the Tsing-í River, and turning northwesterly to Lung-ngan fu, the western side is roughly skirted, while the eastern side returns to Kweichau along the watershed of the River Han. Within this area, life, industry, wealth, prosperity, are all found; outside of it, as a rule, the rivers are unnavigable, the country uncultivable, and the people wild and insubordinate, especially on the south and west.