of the Zone. This arrangement was adopted in 1858 to
establish some sort of commercial equilibrium between the Mexican towns
of the Rio Grande Valley, which were burdened by excessive taxation on
internal trade, and the Texas towns across the river, which at this time
enjoyed a specially low tariff. Consequently prices of food and
manufactured goods were twice or four times as high on the Mexican as on
the American side. The result was persistent smuggling, extensive
emigration from the southern to the northern bank, and the commercial
decline of the frontier states of Mexico, till the Zona Libre adjusted
the commercial discrepancy.[364] Since 1816 a tariff free zone a league
wide has formed the border of French Savoy along the Canton and Lake of
Geneva, thus uniting this canton by a free passway with the Swiss
territory at the upper end of the lake.[365]

[Sidenote: Boundary zones of mingled race elements.]

When the political boundary has evolved by a system of contraction out
of the wide waste zone to the nicely determined line, that line,
nevertheless, is always encased, as it were, in a zone of contact
wherein are mingled the elements of either side. The zone includes the
peripheries of the two contiguous racial or national bodies, and in it
each is modified and assimilated to the other. On its edges it is
strongly marked by the characteristics of the adjacent sides, but its
medial band shows a mingling of the two in ever-varying proportions; it
changes from day to day and shifts backward and forward, according as
one side or the other exercises in it more potent economic, religious,
racial, or political influences.

Its peripheral character comes out strongly in the mingling of
contiguous ethnic elements found in every frontier district. Here is
that zone of transitional form which we have seen prevails so widely in
nature. The northern borderland of the United States is in no small
degree Canadian, and the southern is strongly Mexican. In the Rio Grande
counties of Texas, Mexicans constituted in 1890 from 27 to 55 per cent.
of the total population, and they were distributed in considerable
numbers also in the second tier of counties. A broad band of French and
English Canadians overlaps the northern hem of United States territory
from Maine to North Dakota.[366] In the New York and New England counties
bordering on the old French province of Quebec, they constitute from 11
to 22 per cent. of the total populatio