As indicated later on in this paper, ecological formations tend to develop in cyclic fashion. A period of time within which a given ecological formation develops and culminates is the time period for that particular formation. The length of these time periods may be ultimately measured and predicted, hence the inclusion of the temporal element in the definition. Footnote 33: The word “position” is used to describe the place relation of a given community to other communities, also the location of the individual or institution within the community itself. Footnote 34: Park and Burgess, _Introduction to the Science of Sociology_, p. 509. Footnote 35: Although the actions of individuals may be designed and controlled, the total effect of individual action is neither designed nor anticipated. Footnote 36: _Human Geography_, p. 52. Footnote 37: Brunhes points out by a series of maps the very intimate relation between the distribution of human habitations and the water systems of different countries. He also demonstrates the relation of the modern industrial community to the regions of coal deposits. Footnote 38: The close relation existing between the coal and iron areas and the location of modern industrial communities has frequently been pointed out. L. C. A. Knowles says: “Apart from special and exceptional circumstances industry in Europe and the United States tends to grow up within easy railway access to the great coal areas and on these areas the population is massed in towns” (_The Industrial and Commercial Revolutions in Great Britain during the Nineteenth Century_, p. 24). Footnote 39: To be sure, if the interests in question are commercialized, the growth of the community is subject to the same laws of competition as the other types of communities, with the exception that change is likely to be more rapid and fanciful. Footnote 40: See H. P. Douglass, _The Little Town_, p. 44. Footnote 41: F. E. Clements, _Plant Succession_, p. 3. Carr-Saunders refers to the point of population adjustment to resources as the “optimum.” Footnote 42: J. Russell Smith, _Industrial and Commercial Geography_ (1913), p. 841. Footnote 43: A. T. Hadley, “Economic Results of Improvement in Means of Transportation,” quoted in Marshall, _Business Administration_, p. 35. Footnote 44: L. C. A. Knowles, _The Industrial and Commercial Revolutions in Great Britain during the Nineteenth Century_ (1921), p. 216. Footnote 45: See Gillette, _Rural Sociology_ (1922), pp. 472–73. Footnote 46: For a good statistical summary of the decline in village population in the United States from 1900 to 1920 see Gillette, _op. cit._ (1922), p. 465. Footnote 47: Warren H. Wilson, “Quaker Hill,” quoted in Sims, _Rural Community_, p. 214. Footnote 48: In actual count of some thirty-odd communities in and around Seattle this was about the sequence of development.