These advantages it shares in some degree with the Indian Ocean, which,
as Ratzel justly argues, is not a true ocean, at best only half an
ocean. North of the equator, where it is narrowed and enclosed like an
inland sea, it loses the hydrospheric and atmospheric characteristics of
a genuine ocean. Currents and winds are disorganized by the
close-hugging lands. Here the steady northeast trade wind is replaced by
the alternating air currents of the northeast and southwest monsoons,
which at a very early date[573] enabled merchant vessels to break away
from their previous slow, coastwise path, and to strike a straight
course on their voyage between Arabia or the east coast of Africa and
India.[574] Moreover, this northern half of the Indian Ocean looks like a
larger Mediterranean with its southern coast removed. It has the same
east and west series of peninsulas harboring differentiated
nationalities, the same northward running recesses, but all on a larger
scale. It has linked together the history of Asia and Africa; and by the
Red Sea and Persian Gulf, it has drawn Europe and the Mediterranean
into its sphere of influence. At the western corner of the Indian Ocean
a Semitic people, the Arabs of Oman and Yemen, here first developed
brilliant maritime activity, like their Phoenician kinsmen of the
Lebanon seaboard. Similar geographic conditions in their home lands and
a nearly similar intercontinental location combined to make them the
middlemen of three continents. Just as the Phoenicians, by way of the
Mediterranean, reached and roused slumberous North Africa into
historical activity and became the medium for the distribution of
Egypt's culture, so these Semites of the Arabian shores knocked at the
long-closed doors of East Africa facing on the Indian basin, and drew
this region into the history of southern Asia. Thus the Africa of the
enclosed seas was awakened to some measure of historical life, while the
Africa of the wide Atlantic slept on.

[Sidenote: The sea route to the Orient.]

From the dawn of history the northern Indian Ocean was a thoroughfare.
Alexander the Great's rediscovery of the old sea route to the Orient
sounds like a modern event in relation to the gray ages behind it. Along
this thoroughfare Indian colonists, traders, and priests carried the
elements of Indian civilization to the easternmost Sunda Isles; and
Oriental wares, sciences and religions moved westward to the margin of
Europe and Africa.