erica is the average derived from extensive lowlands in close
juxtaposition to high plateaus capped by lofty mountain ranges. Such
mathematical generalizations indicate the general mass of the
continental upheaval, but not the way this mass is divided into low and
high reliefs.[1026]

The method of anthropo-geography is essentially analytical, and
therefore finds little use for general orometric statements, which may
be valuable to the science of geo-morphology with its radically
different standpoint. For instance, geo-morphology may calculate from
all the dips and gaps in the crest of a mountain range the average
height of its passes, Anthropo-geography, on the other hand,
distinguishes between the various passes according as they open lines of
greater or less resistance to the historical movement across the
mountain barriers. It finds that one deep breach in the mountain wall,
like the Mohawk Depression[1027] and Cumberland Gap in the Appalachian
system,[1028] Truckee Pass in the Sierra Nevada[1029] and the Brenner in
the Alps,[1030] has more far-reaching and persistent historical
consequences than a dozen high-laid passes that only notch the crest.
Pack-trail, road and railroad seek the former, avoid the latter; one
draws from a wide radius, while the other serves a restricted local
need. Therefore anthropo-geography, instead of clumping the passes,
sorts them out, and notes different relations in each.

[Sidenote: Distribution of reliefs.]

In continents and countries the anthropo-geographer looks to see not
what reliefs are present, but how they are distributed; whether
highlands and lowlands appear in unbroken masses as in Asia, or
alternate in close succession as in western Europe; whether the
transition from one to the other is abrupt as in western South America,
or gradual as in the United States. A simple and massive land structure
lends the same trait of the simple and massive to every kind of
historical movement, because it collects the people into large groups
and starts them moving in broad streams, as it were. This fact explains
the historical preponderance of lowland peoples and especially of steppe
nomads over the small, scattered groups inhabiting isolated mountain
valleys. The island of Great Britain illustrates the same principle on a
small scale in the turbid, dismembered history of independent Scotland,
with its Highlanders and Lowlanders, its tribes and clans separated by
mountains, gorges, str