Among the mountainous districts many small lakes are found, a few of which are large enough to be navigated. In Yezo there are six considerable lakes. In the Main island the largest lake is Biwa, in the beautiful mountain region north of Kyōto. It received its name from its fancied resemblance to the shape of a musical instrument called a _biwa_. There is a legend that this lake came into existence in a single night, when the volcanic mountain Fuji-san 300 miles distant was raised to its present height. It is about fifty miles long and about twenty miles broad at its greatest width. It is said to be not less than 330 feet at its greatest depth. It is navigated by steamboats and smaller craft. It is situated about 350 feet above the ocean. Lake Suwa in Shinano is 2,635 feet above the ocean. Lake Chūzenji in the Nikkō mountains is 4,400 feet; and Hakoné lake near Yokohama is 2,400 feet. Owing to the narrowness of the Main island, there are no rivers of a large size. Most of them take their rise in the mountainous regions of the middle of the islands, and by a more or less circuitous route find their way to the ocean. The Tone-gawa (_gawa_ means river) is the longest and broadest of the rivers of Japan. It rises in Kōtsuke and flows in an eastern direction, receiving many tributaries, attains a breadth of more than a mile, and with a current much narrowed, empties into the Pacific ocean at Chōshi point. It is about 170 miles long and is navigated by boats for a great distance. The Shinano-gawa, which may be named as second in size, rises in the province of Shinano, flows in a northern direction, and empties into the Japan sea at Ni-igata. The Kiso-gawa also rises in the high lands of Shinano, and, flowing southward, empties into Owari bay. The Fuji-kawa(9) takes its rise in the northern part of the province of Kai, and in its course skirting the base of Fuji-san on the west, empties into Suruga bay. It is chiefly notable for being one of the swiftest streams in Japan and liable to sudden and great floods. To these rivers may be added the Yodo-gawa, which is the outlet of Lake Biwa, in the province of Ōmi, and which flows through Kyōto, and empties into the Inland sea at Ōsaka. This river is navigable for flat-bottomed steamboats as far as Kyōto. In the islands of Kyūshū and Shikoku there are no large rivers; but there are many streams which give to these islands their richness and fertility.