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