just here that we find certain northern traces of Southeastern culture. In the Mississippi Valley these same lowlands reach up to the Ohio and the Missouri, and here also, we find the margin of Southeastern traits. The two types of culture which we find in the Bison area (1), the western and the eastern, line up along the north and south divide of 2,000 feet. Further, it is distinctly among the eastern tribes that we find Eastern Woodland traits, the elevation of both being below 2,000 feet.
These few illustrations must suffice, but the reader can follow out others by referring to suitable maps. We are not contending for a direct correlation between elevation and culture, for these numerals are but convenient geographical indices to climatic, faunal, and floral areas. As boundaries, they are just as arbitrarily chosen as those for culture areas, but for that very reason should be strictly comparable. The fact, then, that they do so correspond cannot be dismissed as a logical error. We are thus brought to the conclusion that the phenomena of our subject manifest a strong tendency to expand to the limits of the geographical area in which they arise, and no farther. Language and blood seem to spill over the edges far more readily than culture, from which we must infer that their dispersion is a by-product of migration, but that these migratory groups seem unable to resist complete cultural assimilation.
From this point of view, it is conceivable that the Muskhogean and Algonkian stocks, for instance, could have exchanged habitats without changing the cultures localized within the two areas, provided the shifting was by successive small units; or that all of the Shoshonean peoples could have become Pueblos and the Keresan and other stocks have scattered out on the plateaus to the north, while the culture values of the two areas remained relatively the same. That such extreme transpositions ever occurred is, of course, improbable, but their possibility is demonstrated in the Plains and particularly in the Pueblo area itself.
Yet, the real problem in the case remains unsolved. What became of the culture brought into an area by the first
