cance of deterioration]

This is the effect of climate which has had the most far-reaching and
persistent historical consequences. Our study of the historical
movements of peoples in the northern hemisphere revealed a steady influx
from colder into tropical and sub-tropical lands, followed always by
enervation and loss of national efficiency, due partly to the
debilitating heat of the new habitat, partly to its easier conditions of
living, whether the intruders came as conquerors and appropriated the
fat of the land, or as immigrant colonists who dropped into slack
methods of agriculture, because rain and sun and soil made their
reluctant labor scarcely necessary. Everywhere in the Tropics the
enervating effects of heat, moisture, and abundance make not only the
natives averse to steady work, but start the energetic European
immigrant down the same easy descent to Avernus. Passing over the
deterioration of the Aryans in India, the Persians in Mesopotamia, and
the Vandals in Africa, we find that modern instances show the
transformation to be very rapid. The French who since 1715 have occupied
the islands of Reunion and Mauritius have lost much of their thrift and
energy, though their new homes lie just within the southern tropic, and
are blessed with an oceanic climate. Yet the volunteer troops sent by
Reunion to aid in the recent subjugation of the Hovas in Madagascar
proved to be utterly useless.[1436] The Spaniards who come to-day to
Mexico have great energy, born of their former hard conditions of life
in Spain. But their children are reared in a country whose mean annual
temperature, even on the plateau, exceeds that of Spain by 10 deg.C. (or
18 deg.F.), a difference equal to that between Mobile and New York, or
Madrid and Christiania. Hence they are less energetic and vigorous,
while the third generation are typical Mexicans in their easy-going way
of life.[1437] The Germans who recently have colonized southern Brazil in
great numbers show a similar deterioration under similar increase of
mean annual temperature, combined with somewhat greater humidity, which
intensifies the debilitating effects of the heat. An investigation made
in 1900 by the International Harvester Company of America revealed the
fact that the German farmer in the State of Santa Catharina rarely
cultivated over one acre of grain.[1438] Much of the iron in the blood and
conscience of the New England missionary stock which went to Hawaii two
gener