Grote_ 260
3. Isolation as an Explanation of National Differences.
_William Z. Ripley_ 264
4. Natural versus Vicinal Location in National Development.
_Ellen C. Semple_ 268

III. Investigations and Problems
1. Isolation in Anthropogeography and Biology 269
2. Isolation and Social Groups 270
3. Isolation and Personality 271

_Bibliography: Materials for the Study of Isolation_ 273
_Topics for Written Themes_ 277
_Questions for Discussion_ 278

CHAPTER V. SOCIAL CONTACTS

I. Introduction
1. Preliminary Notions of Social Contact 280
2. The Sociological Concept of Contact 281
3. Classification of the Materials 282

II. Materials

A. Physical Contact and Social Contact
1. The Frontiers of Social Contact. _Albion W. Small_ 288
2. The Land and the People. _Ellen C. Semple_ 289
3. Touch and Social Contact. _Ernest Crawley_ 291

B. Social Contact in Relation to Solidarity and to Mobility
1. The In-Group and the Out-Group. _W. G. Sumner_. 293
2. Sympathetic Contacts versus Categoric Contacts. _N. S. Shaler_ 294
3. Historical Continuity and Civilization. _Friedrich Ratzel_ 298
4. Mobility and the Movement of Peoples. _Ellen C. Semple_ 301

C. Primary and Secondary Contacts
1. Village Life in America (from _the Diary of a Young Girl_).
_Caroline C. Richards_ 305
2. Secondary Contacts and City Life. _Robert E. Park_. 311
3. Publicity as a Form of Secondary Contact. _Robert E. Park_ 315
4. From Sentimental to Rational Attitudes. _Werner Sombart_ 317
5. The Sociological Significance of the "Stranger." _Georg Simmel_ 322

III. Investigations and Problems
1. Physical Contacts 327
2. Touch and the Primary Contacts of Intimacy 329
3. Primary Contacts of Acquaintanceship 33