from one another, southeastward and southwestward. In the centers
of the continents they expand into vast plateaus. That of America
in the Rocky Mountain region of the United States reaches a width
of over a thousand miles, while that of Asia in Tibet and western
China expands to far greater proportions.

From the plateaus the two cordilleras swing abruptly Atlantic-
ward. The Eurasian cordillera extends through the Hindu Kush,
Caucasus, and Asia Minor ranges to southern Europe and the Alps.
Then it passes on into Spain and ends in the volcanoes of the
Canary Islands. The American cordillera swings eastward in Mexico
and continues as the isolated ranges of the West Indies until it
ends in the volcanoes of Martinique. Central America appears at
first sight to be a continuation of the great cordillera, but
really it is something quite different--a mass of volcanic
material poured out in the gap where the main chain of mountains
breaks down for a space. In neither hemisphere, however, is the
main southward sweep of the mountains really lost. In the Old
World the cordillera revives in the mountains of Syria and
southern Arabia and then runs southward along the whole length of
eastern Africa. In America it likewise revives in the mighty
Andes, which take their rise fifteen hundred miles east of the
broken end of the northern cordillera in Mexico. In the Andes
even more distinctly than in Africa the cordillera forms a mighty
wall running north and south. It expands into the plateau of Peru
and Bolivia, just as its African compeer expands into that of
Abyssinia, but this is a mere incident. The main bone, so to
speak, keeps on in each case till it disappears in the great
southern ocean. Even there, however, it is not wholly lost, for
it revives in the cold, lofty continent of Antarctica, where it