The northern part of the Sea of Japan, which washes the Usuri region, has, besides the smaller bays of Olga and Vladimir, the beautiful Gulf of Peter the Great, on which stands Vladivostok, the Russian naval station on the Pacific. Okhotsk and Ayan on the Sea of Okhotsk, Petropavlovsk on the east shore of Kamchatka, Nikolayevsk, and Vladivostok on the Sea of Japan, and Dui on Sakhalin are the only ports of Siberia.
Crystalline rocks crop out at several capes; Cretaceous limestones, containing an abundant and specific fauna of gigantic ammonites, occur at Dui on the west coast, and Tertiary conglomerates, sandstones, marls and clays, folded by subsequent upheavals, in many parts of the island.
At Dui the average yearly temperature is only 33 .o ° Fahr.
At Alexandrovsk near Dui the annual range is from 8r ° in July to -38° in January, while at Rykovsk in the interior the minimum is -49° Fahr.
Flint implements, exactly like those of Siberia and Russia, have been found at Dui and Kusunai in great numbers, as well as polished stone hatchets, like the European ones, primitive pottery with decorations like those of Olonets and stone weights for nets.