If individual variations “on a flat” were the only kind of variability in language, I believe we should be at a loss to explain why and how dialects arise, why it is that a linguistic prototype gradually breaks up into a number of mutually unintelligible languages.  But language is not merely something that is spread out in space, as it were—­a series of reflections in individual minds of one and the same timeless picture.  Language moves down time in a current of its own making.  It has a drift.  If there were no breaking up of a language into dialects, if each language continued as a firm, self-contained unity, it would still be constantly moving away from any assignable norm, developing new features unceasingly and gradually transforming itself into a language so different from its starting point as to be in effect a new language.  Now dialects arise not because of the mere fact of individual variation but because two or more groups of individuals have become sufficiently disconnected to drift apart, or independently, instead of together.  So long as they keep strictly together, no amount of individual variation would lead to the formation of dialects.  In practice, of course, no language can be spread over a vast territory or even over a considerable area without showing dialectic variations, for it is impossible to keep a large population from segregating itself into local groups, the language of each of which tends to drift independently.  Under cultural conditions such as apparently prevail to-day, conditions that fight localism at every turn, the tendency to dialectic cleavage is being constantly counteracted and in part “corrected” by the uniformizing factors already referred to.  Yet even in so young a country as America the dialectic differences are not inconsiderable.

Under primitive conditions the political groups are small, the tendency to localism exceedingly strong.  It is natural, therefore, that the languages of primitive folk or of non-urban populations in general are differentiated into a great number of dialects.  There are parts of the globe where almost every village has its own dialect.  The life of the geographically limited community is narrow and intense; its speech is correspondingly peculiar to itself.  It is exceedingly doubtful if a language will ever be spoken over a wide area without multiplying itself dialectically.  No sooner are the old dialects ironed out by compromises or ousted by the spread and influence of the one dialect which is culturally predominant when a new crop of dialects arises to undo the leveling work of the past.  This is precisely what happened in Greece, for instance.  In classical antiquity there were spoken a large number of local dialects, several of which are represented in the literature.  As the cultural supremacy of Athens grew, its dialect, the Attic, spread at the expense of the rest, until, in the so-called Hellenistic period following the Macedonian conquest, the Attic