ple, American History and its Geographic Conditions, pp.
280-287. Boston, 1903.

[286] C.E. Akers, History of South America, 1854-1894, pp. 501-502,
556-562. New York, 1904.

[287] E.A. Freeman, Historical Geography of Europe, p. 14. London, 1882.

[288] Helmolt, History of the World, Vol. VI, pp. 125-132, map. New
York, 1902-1906. Ripley, Races of Europe, pp. 274, 297, 308, 472-473.
New York, 1899.

[289] H.J. Mackinder, Britain and the British Seas, pp. 183-191. London,
1904.

[290] W.Z. Ripley, Races of Europe, pp. 26, 353, 361-365. Map. New York,
1899.

[291] Ratzel, History of Mankind, Vol. I, 214-218. London, 1896-1898.

CHAPTER VI

GEOGRAPHICAL AREA

[Sidenote: The size of the earth.]

Every consideration of geographical area must take as its starting point
the 199,000,000 square miles (510,000,000 square kilometers) of the
earth's surface. Though some 8,000,000 square miles (21,000,000 square
kilometers) about the poles remain unexplored, and only the twenty-eight
per cent. of the total constituting the land area is the actual habitat
of man, still the earth as a whole is his planet. Its surface fixes the
limits of his possible dwelling place, the range of his voyages and
migrations, the distribution of animals and plants on which he must
depend. These conditions he has shared with all forms of life from the
amoeba to the civilized nation. The earth's superficial area is the
primal and immutable condition of earth-born, earth-bound man; it is the
common soil whence is sprung our common humanity. Nations belong to
countries and races to continents, but humanity belongs to the whole
world. Naught but the united forces of the whole earth could have
produced this single species of a single genus which we call Man.

[Sidenote: Relation of area to life.]

The relation of life to the earth's area is a fundamental question of
bio-geography. The amount of that area available for terrestrial life,
the proportion of land and water, the reduction or enlargement of the
available surface by the operation of great cosmic forces, all enter
into this problem, which changes from one geologic period to another.
The present limited plant life of the Arctic regions is the impoverished
successor of a vegetation abundant enough at the eighty-third parallel
to produce coal. That was in the Genial Period, when the northern
hemisphere with its broad land-masses presented a far larger area for
the support of life t