nvestigating the reason for the small number of
reaping machines employed in Argentine in proportion to the area under
cultivation, found that the simple climatic condition of a long growing
season enabled one reaper to serve about twice the acreage usual in the
United States, because it could work twice as long.[1449]

[Sidenote: Zones of culture.]

Over and beyond slight local variations of climate and season within the
same zone, which contribute their quota to economic and historical
results, it is the fundamental differences between the hot, cold and
temperate climatic zones that produce the most conspicuous and abiding
effects. These broad belts, each with its characteristic climatic
conditions and appropriate civilization, form so many girdles of culture
around the earth. They have their dominant features of heat and cold,
variously combined with moisture and aridity, which give a certain zonal
stamp to human temperature and development.

The two cold belts have little claim to the name of cultural zones,
since their inability to support more than an insignificant population
has made them almost a negligible factor in history. [Compare maps pages
8, 9, and 612.] The discoveries and settlements of the Northmen in
Greenland remained a barren historical event, though the vikings' ships
reached a new hemisphere. Iceland is the only land in this sub-arctic
region which ever figured upon the stage of history; and its role was
essentially passive. Such prominence as it acquired was due to its
island nature and its situation in a swirl of the Gulf Stream, which
ameliorates the worst climatic effects of its far northern location, and
brings it just within the upper limit of the temperate belt. The wide
sub-arctic lowlands of Russia and Siberia, which, from the Ural
Mountains to the lower Amur River, stretch the cold zone well below the
sixtieth parallel, have at times in the last three centuries and
especially in the past decade thrown their great mass into the scale of
eastern Asiatic history. This has been possible because the hot summer
characteristic of continental climates forces the July isotherm of 20 deg.C.
northward over the vast heated surface of Asia nearly to the sixtieth
parallel, well within the borders of Siberia. It gives that belt the
short but warm growing season with protracted hours of sunshine which
is so favorable to cereals, lending to Omsk, Tomsk, Vitimsk and all the
stretch of Russian settlement