. The
Piraeus, which had been the heart of ancient Athens, almost wholly lost
its value in the checkered political history of the country during the
Middle Ages, when naval power and merchant marine almost vanished; but
with the restoration of Grecian independence in 1832, much of its
pristine activity was restored. Up to the beginning of the seventeenth
century, Japan had exploited her advantageous location and her richly
indented coast to develop a maritime trade which extended from Kamchatka
to India; but in 1624 an imperial order withdrew every Japanese vessel
from the high seas, and for over two hundred years robbed her busy
littoral of all its historical significance. The real life of the
Pacific coast of the United States began only with its incorporation
into the territory of the Republic, but it failed to attain its full
importance until our acquisition of Alaska, Hawaii, and the Philippines.
So the coast of the Persian Gulf has had periods of activity alternating
with periods of deathlike quiet. Its conquest by the Saracens in the
seventh century inaugurated an era of intense maritime enterprise along
its drowsy shores. What new awakening may it experience, if it should
one day become a Russian littoral!

[Sidenote: Physical causes of decline.]

Sometimes the decline in historical importance is due to physical
modifications in the coast itself, especially when, the mud transported
by a great river to the sea is constantly pushing forward the outer
shoreline. The control of the Adriatic passed in turn from Spina to
Adria, Ravenna, Aquileia, Venice, and Trieste, owing to a steady silting
up of the coast.[525] Strabo records that Spina, originally a port, was
in his time 90 stadia, or 10 miles, from the sea.[526] Bruges, once the
great _entrepot_ of the Hanseatic League, was originally on an arm of
the sea, with which it was later connected by canal, and which has been
silted up since 1432, so that its commerce, disturbed too by local wars,
was transferred to Antwerp on the Scheldt.[527] Many early English
ports on the coast of Kent and on the old solid rim of the Fenland
marshes now lie miles inland from the Channel and the Wash.

A people never utilizes all parts of its coast with equal intensity, or
any part with equal intensity in all periods of its development; but,
according to the law of differentiation, it gradually concentrates its
energies in a few favored ports, whose maritime business tends to becom