h-rate due partially to improved
housing conditions, progress in personal hygiene of the poorer classes
and in city sanitation and inspection; (2) by migration: that is,
short distance movements by progressive stages from the more rural
districts toward the larger centers.[31] In the case of the great
cities this may mean increase in density of the most populated
areas.[32]

The causes of concentration in cities are the following:

I. The Divorce of Men from the Soil.[33] The diminishing relative
importance of elementary wants, improvements in scientific cultivation
and in agricultural machinery, and the opening of distant and virgin
fields by better transportation have reduced the relative number of
workers needed on the soil.

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 agglomerat