The Japanese islands are invested on the east by the Pacific ocean. They are separated from the continent by the Okhotsk sea, the Japan sea, and the Yellow sea. The Kuro Shiwo (black current) flows from the tropical waters in a northeast direction, skirting the islands of Japan on their east coasts, and deflecting its course to the eastward carries its ameliorating influences to the west coast of America. It is divided by the projecting southern extremity of the island of Kyūshū, and a perceptible portion of it flows on the west coast of the Japanese islands through the Japan sea and out again into the Pacific ocean through the Tsugaru and the La Perouse straits. The effect of the Kuro Shiwo upon the climate and productions of the lands along which it flows is not greatly different from that of the Gulf Stream in the Atlantic ocean, which in situation, direction, and volume it resembles. The body of water known among foreigners as the Inland sea, but which the Japanese call Seto-no-Uchi-Umi (the sea within the straits), is a picturesque sheet of water situated between the Linschoten straits on the east and the Shimonoseki straits on the west. The latter is seven miles long and at its narrowest part not more than two thousand feet wide. It separates Kyūshū on the south from the Main island on the north. The Inland sea is occupied by an almost countless number of islands, which bear evidence of volcanic origin, and are covered with luxuriant vegetation. The lines of steamers from Shanghai and Nagasaki to the various ports on the Main island, and numberless smaller craft in every direction, run through the Inland sea. The principal islands of Japan are interspersed with mountains, hills and valleys. Yezo the most northern of these islands is traversed by two ranges of mountains; the one being the extension of the island of Saghalien, the other the extension of the Kurile islands. These two ranges cross each other at the centre of the island, and here the greatest elevation is to be found. The shape given to the island by these intersecting ranges is that of a four-pointed star. The rivers in nearly all cases flow from the centre outward to the sea. There are few large rivers. The most important is the Ishikari which empties into Ishikari bay. The valley of this river is the most rich and fertile part of the island.