Inner asia may be described as a group of regions that have neither a frontage on the s a nor navigable rivers leading to the sea. Under this definition northern, but not southern Iran, and western, but not eastern, Manchuria may be regarded as Inner Asian regions. Most of Inner Asia either touches or stands astride of the Soviet frontier in Asia?the longest frontier in the world, stretching from Turkey to Korea. Tibet, lying distant from Russia, is a notable exception to this rule. An important characteristic of Inner Asia is that most of its political frontiers do not mark the edges of territories inhabited by peoples who differ from each other in language, economic activity, social organization, and in the kind of group loyalty that is founded on a feeling of kinship. They divide kindred peoples from each other and place them under different political sovereignties. As a consequence there is an important difference in the political geography of the frontier zone as between Inner Asian regions and other regions; in Western Europe, for example, where different peoples have lived in adjoining territories for many centuries. This contrast is shown diagrammatically for the French-German frontier in Figure i, and for the Russian-Mongol-Chinese frontier in Figure 2. Both sketches are drawn to illustrate a phenomenon of great importance in political geography: the fact that the difference between two neighbouring peoples is usually no where near as sharp as the drawn on the map. Normally, the frontier line is in fact a legal abstraction; what exists on the ground is not a but a zone?but there can be more than one kind of zone. A man going on foot from France to Germany, walking not more than 20 or 30 miles a day, finds himself at first among people who, allowing for pro? vincial differences, may be called standard Frenchmen. As he goes along, he finds a gradual increase in the intermingling of those characteristics that, taken as a group or complex, we call German and those we call French; first a larger number of loan-words in the local dialect, then more bilingual people; a gradual increase, in territory politically French, of house-types and cultivation practices that are usually associated with Germany, and so on. At or near the frontier of the map he finds the maximum intermingling of French and German; then, as he goes on, a shading off through Germans with decreasing marks of French influence, until he is among standard Germans.1 Figure 1