The Chinese nation, again, owes its existence and its homogeneity of mental and physical type to geographical unity. Roughly, China consists of the basins of two immense rivers, not separated from one another by any great physical barrier, but forming a compact territory well marked off save in the north. It comprises no such partially separate areas as in Europe are constituted by Spain, or Italy, or Greece, or Scandinavia, or even France; almost all parts are well adapted for agriculture. Hence, largely, the national unity and the national sentiment which have long existed, and possibly a latent capacity for national thought and action. Perhaps the most striking instance of all is ancient Egypt. There, in the long strip of land rendered fertile by the waters of the Nile, a people of mixed origin was long shut up and isolated; there all men felt their immediate dependence on the same great powers, the great river which once a year overflows its banks, and the scorching sun which passes every day across a cloudless sky. There all men looked out on the same unvarying and unvaried landscape, hoped and feared for the same causes, suffered the same pains, prayed for the same goods. There was formed one of the most stable and enduring of nations, whose uniform culture certainly bears the impress of the uniform monotonous physical environment[66]. The other way in which physical environment affects homogeneity is by determining similarity or difference of occupations and, through them, similarities or differences of practical interests and of acquired qualities. So long as such differences are determined in many small areas, the result is merely a greater differentiation of the parts, without danger to the unity of the whole nation. But, when the physical differences divide a whole people into two or more locally separate groups differing in occupation and interests and habits, they endanger the unity of the whole. There are to-day many countries in which the distribution of mineral wealth is exerting an influence of this sort, giving rise to the differentiation of an industrial area from agricultural areas and a consequent divergence of interests and of mental habits; notably South Africa, Spain, and Italy.