TRANSPORTATION 245

sparsely settled upriver country, from which raw materials flowed down
to the more densely inhabited region around the river's mouth. Only as
sail-driven craft capable of moving heavy goods up-river developed was
there a significant spreading of Egyptian culture and people along the
entire course of the lower Nile. Here is perhaps the first clear instance in
which one mode of transport led to a concentration of population and
another to a relative decentralization of that population.

The varied ecological effects of different transportation techniques has
subsequently appeared over and over in different societies. New Orleans,
for example, was the cultural and commercial center of the Mississippi
valley when all goods flowed down-river via barge and raft; it was pushed
into a secondary position when the steamboat brought cheap upriver
haulage and expanded the role of such upriver cities as St. Louis.

The Sumerians used ships of considerable size on the Persian Gulf as
early as 7000 B.C., and by 1200 B.C. the Egyptians were using large sail
and oar-driven ships on the Nile and the Red Sea. "The civilizations of
Crete, Greece, Carthage, and finally Rome depended largely upon water-
transported goods and therefore upon the ship. Shipbuilding techniques
reached a peak of development about the opening of the Christian Era
and were not significantly improved upon until long after the arts of ship-
building had been rediscovered in western Europe during the Middle
Ages. The "Santa Maria," in which Columbus discovered the Americas,
was fabricated in much the same way as had been the grain-transporting
ships of Rome over two thousand years before.1

Up to the Christian Era ship designing had not, however, kept pace
with shipbuilding technology. The ships of the Romans, as those of the
Egyptians had been, were shallow draught and propelled mainly by oar,
an advantage in the frequently becalmed Mediterranean but a marked
handicap elsewhere. Sails were used only for running with the wind, and
the shallow-draught ships were so subject to adverse weather that it
was the normal practice to follow coastlines by day and tie up in a
harbor at night.

The invention of the deep keel, which permitted the sailing ship to
move upwind by tacking and which gave the ship great stability and
comparative security in storms, seems to have occurred in northern Eu-
rope sometime after the beginning of the Christian Era. About the eleventh
century it was introduced to western Europeans by the Norsemen or
some related people who, although they used the deep keel, did not con-
struct ships of any considerable size. The Spanish, the Portuguese, and
some other western Europeans combined the deep keel with the redis-
covered arts of Mediterranean shipbuilding, so that by the fourteenth

'-See C. Torr, Ancient Ships (Routledge, London, 1918).