Among the many branches of this great basin are the _Gallic Sea_,
running north toward Gaul, between Spain and the islands of Sardinia and
Corsica, forming the stormy Gulf of the Lion and that of Genoa; the
_Tyrrhenian Sea_, between Sardinia and Italy; the _Ionian Sea_ and the
_Adriatic_ running north from it, between Italy and the Balkan
peninsula, towards the ancient seaport of Adria, perhaps the oldest in
Europe.
Beyond Greece, the island-studded Ægean leads north to the narrow inlet
of the _Dardanelles_, opening into the little Sea of Marmora, named from
its marble-yielding islands, and from that by the _Bosporus_ or Oxford
(the canal of Constantinople), into the second great Mediterranean
basin, the _Black Sea_ or Euxine, with its offshoot the shallow _Sea of
Azof_. The Caspian Sea, forms part of the natural frontier between
Europe and Asia.
The indented seaboard of Europe measures not less than sixty thousand
miles.