development of, its customary significance. In the preceding chapter
the point was made that the distinction between isolation and contact is
not absolute but relative. Members of a society spatially separate, but
socially in contact through sense perception and through communication
of ideas, may be thereby mobilized to collective behavior. Sociological
interest in this situation lies in the fact that the various kinds of
social contacts between persons and groups determine behavior. The
student of problems of American society, for example, realizes the
necessity of understanding the mutual reactions involved in the contacts
of the foreign and the native-born, of the white and the negro, and of
employers and employees. In other words, contact, as the first stage of
social interaction, conditions and controls the later stages of the
process.

It is convenient, for certain purposes, to conceive of contact in terms
of space. The contacts of persons and of groups may then be plotted in
units of _social distance_. This permits graphic representation of
relations of sequence and of coexistence in terms both of units of
separation and of contact. This spatial conception may now be applied to
the explanation of the readings in social contacts.

3. Classification of the Materials

In sociological literature there have grown up certain distinctions
between types of social contacts. Physical contacts are distinguished
from social contacts; relations within the "in-group" are perceived to
be different from relations with the "out-group"; contacts of historical
continuity are compared with contacts of mobility; primary contacts are
set off from secondary contacts. How far and with what advantage may
these distinctions be stated in spatial terms?

a) _Land as a basis for social contacts._--The position of persons and
peoples on the earth gives us a literal picture of the spatial
conception of social contact. The cluster of homes in the Italian
agricultural community suggests the difference in social life in
comparison with the isolated homesteads of rural America. A gigantic
spot map of the United States upon which every family would be indicated
by a dot would represent schematically certain different conditions
influencing group behavior in arid areas, the open country, hamlets,
villages, towns, and cities. The movements of persons charted with
detail sufficient to bring out variations in the daily, weekly, monthly,
and year