II. The Growth of Commercial Centers.[34] This went hand in hand with the Agrarian Revolution. Trade has been the basis of city founding. The prevailing influence in determining location has been "_a break in transportation_." Where goods are transferred and where, in addition, ownership changes hands, urban centers grow up. Wealthy classes arise which require others to supply their increasing and varied wants. III. The Growth of Industrial Centers.[35] The passage of industry from the household, handicrafts and domestic systems to that of the factory, with the invention of power machinery and modern methods of transportation and communication, draws population away from the rural districts to the industrial centers. IV. Secondary or Individual Causes.[36] (a) The shifting demand for transfer of labor from agricultural to industrial production was met by the economic motive of workers. (b) Political action has influenced city growth; legislation affecting trade and the migration of labor; centralization of governmental machinery in the cities; legal forms of land tenure, _etc._ (c) Social advantages such as better education, varied amusements, higher standard of living, intellectual associations and pursuits, draw people to urban centers, while desire for the contact of the moving crowds, for the excitement and apparent ease of city life, serve to make the rural districts distasteful. FOOTNOTES: [1] The most comprehensive study of city growth is _The Growth of Cities in the 19th Century_, by A.F. Weber, vol. xi, _Columbia University Studies in History, Economics and Public Law_ (New York, 1899), pp. 1-478. The meaning of city and urban population is that used by Weber: An agglomerated population of two thousand to ten thousand for towns, more than ten thousand for cities, more than one hundred thousand for great cities. _Cf._ p. 16. [2] See footnote at the end of this chapter. Weber, _op. cit._, pp. 146-154. [3] Weber, _op. cit._, pp. 167-68; 173-74; 201-207. See also footnote at end of chapter. [4] Twelfth Census, _Bulletin 8, Negroes in the United States_, p. 29. [5] Weber, _op. cit._, pp. 24-27, 162. [6] Coman, _Industrial History of the United States_, Revised edition, (New York, 1910), pp. 308-9. [7] Kelsey, The Negro Farmer, (Chicago, 1903), pp. 5-103; _vide_ pp. 24-28. Du Bois, _The Negro Farmer_ in _Bulletin 8_, (Twelfth Census), pp. 79-81. [8] DuBois, _op. cit._, p. 77. [9] Kelsey, _Some Causes of Negro Emigration: Charities_, New York, vol. xv, no. 1, pp. 15-17; _cf._ DuBois, _op. cit._, pp. 73-74. [10] _Statistical Abstract of the United States, 1909, table 143_, p. 261. [11] Kellor. _Out of Work_, pp. 73, 83. [12] Cf. Tucker, _Negro Craftsmen in New York_, in _Southern Workman_, September, 1907, p. 550.