The map undertakes to show the habitat of the linguistic families only, and this is for but a single period in their history, viz, at the time when the tribes composing them first became known to the European, or when they first appear on recorded history. As the dates when the different tribes became known vary, it follows as a matter of course that the periods represented by the colors in one portion of the map are not synchronous with those in other portions. Thus the data for the Columbia River tribes is derived chiefly from the account of the journey of Lewis and Clarke in 1803-’05, long before which period radical changes of location had taken place among the tribes of the eastern United States. Again, not only are the periods represented by the different sections of the map not synchronous, but only in the case of a few of the linguistic families, and these usually the smaller ones, is it possible to make the coloring synchronous for different sections of the same family. Thus our data for the location of some of the northern members of the Shoshonean family goes back to 1804, a date at which absolutely no knowledge had been gained of most of the southern members of the group, our first accounts of whom began about 1850. Again, our knowledge of the eastern Algonquian tribes dates back to about 1600, while no information was had concerning the Atsina, Blackfeet, Cheyenne, and the Arapaho, the westernmost members of the family, until two centuries later. Notwithstanding these facts, an attempt to fix upon the areas formerly occupied by the several linguistic families, and of the pristine homes of many of the tribes composing them, is by no means hopeless. For instance, concerning the position of the western tribes during the period of early contact of our colonies and its agreement with their position later when they appear in history, it may be inferred that as a rule it was stationary, though positive evidence is lacking. When changes of tribal habitat actually took place they were rarely in the nature of extensive migration, by which a portion of a linguistic family was severed from the main body, but usually in the form of encroachment by a tribe or tribes upon neighboring territory, which resulted simply in the extension of the limits of one linguistic family at the expense of another, the defeated tribes being incorporated or confined within narrower limits. If the above inference be correct, the fact that different chronologic periods are represented upon the map is of comparatively little importance, since, if the Indian tribes were in the main sedentary, and not nomadic, the changes resulting in the course of one or two centuries would not make material differences. Exactly the opposite opinion, however, has been expressed by many writers, viz, that the North American Indian tribes were nomadic. The picture presented by these writers is of a medley of ever-shifting tribes, to-day here,