2. Every addition in numbers and expansion of the city area is accompanied by the redistribution and re-allocation of the whole population. Some elements are given a new locus, while others shift but little as a result of the stimulus incident to the arrival of newcomers. This redistribution of the city population has become a constantly operating process in view of the constant growth of the city either through natural increase of the population or through migration from without. Allison, Thomas W. “Population Movements in Chicago,” _Jour. of Social Forces_, II (May, 1924), 529–33. (V, 1, 3; VII, 4.) Aurousseau, M. “Distribution of Population: A Constructive Problem,” _Geog. Rev._, XI (October, 1921), 568–75. “Density concerns itself with the number of people per unit of area; distribution deals with the comparative study of density from area to area; and arrangement considers the way in which people are grouped. Grouping is the fundamental concept....” (I, 1; IV, 1; X, 2.) Bushee, F. A. “Ethnic Factors in the Population of Boston,” _Pub. Amer. Statistical Assoc._, Vol. IV, No. 2, pp. 307–477. (V, 1, 2, 3.) Douglas, H. Paul. _The Suburban Trend_ (New York, 1925). Traces the movement toward decentralization in the larger American urban communities. (VII, 2, 1, 4; IV, 2; III, 5; V, 4.) Hirschfeld, Magnus. _Berlins drittes Geschlecht_, Vol. III in “Grossstadt Dokumente” (Berlin, 1905). A study of the homosexuals in Berlin as a sample of the grouping of population in the large city. (V, 1, 3; VII, 5.) Hooker, G. E. “City-Planning and Political Areas,” _Nat. Mun. Rev._, VI (May, 1917), 337–45. (IV, 3; V, 1, 4, 5; VI, 7.) The London Society. _The London of the Future_ (New York and London, 1921). An excellent view of the processes bringing about the allocation of the population and the trend of growth of the city from the core pressing outward toward the periphery. (II, 3; III, 1, 5, 6; IV; V; VI; VII; VIII, 1, 2, 3; IX, 1, 2, 3, 4.) Ripley, W. Z. “Racial Geography of Europe,” _Popular Science Monthly_, LII (1898), 591–608; XIV, “Urban Problems.” See also his “Races of Europe,” chap. xx, on “Ethnic Stratification and Urban Selection.” (V, 3.) Salten, Felix. _Wiener Adel_, Vol. XIV in “Grossstadt Dokumente” (Berlin, 1905). Shows the local grouping of the nobility in the large European city. (IX, 4.) Schmid, Herman. _City bildung und Bevölkerungsverteilung in Grossstädten: Ein Beitrag zur Entwicklungsgeschichte des modernen Städtewesens_ (München, 1909). Shows that the normal process of growth of the city is by emptying at the center, and redistributing its population around the periphery. (Compare Mark Jefferson, “The Anthropography of Some Great Cities: A Study in Distribution of Population,” _Bull. Amer. Geog. Soc._, XLI (1909), 537–66. (VII, 4, 5.))