JAMAICA, the largest island in the British West Indies. It lies about 80 m. S. of the eastern extremity of Cuba, between 17° 43´ and 18° 32´ N. and 76° 10´ and 78° 20´ W., is 144 m. long, 50 m. in extreme breadth, and has an area of 4207 sq. m. The coast-line has the form of a turtle, the mountain ridges representing the back. A mountainous backbone runs through the island from E. to W., throwing off a number of subsidiary ridges, mostly in a north-westerly or south-easterly direction. In the east this range is more distinctly marked, forming the Blue Mountains, with cloud-capped peaks and numerous bifurcating branches. They trend W. by N., and are crossed by five passes at altitudes varying from 3000 to 4000 ft. They culminate in Blue Mountain Peak (7360 ft.), after which the heights gradually decrease until the range is merged into the hills of the western plateau. Two-thirds of the island are occupied by this limestone plateau, a region of great beauty broken by innumerable hills, valleys and sink-holes, and covered with luxuriant vegetation. The uplands usually terminate in steep slopes or bluffs, separated from the sea, in most cases, by a strip of level land. On the south coast, especially, the plains are often large, the Liguanea plain, on which Kingston stands, having an area of 200 sq. m. Upwards of a hundred rivers and streams find their way to the sea, besides the numerous tributaries which issue from every ravine in the mountains. These streams for the most part are not navigable, and in times of flood they become devastating torrents. In the parish of Portland, the Rio Grande receives all the smaller tributaries from the west. In St Thomas in the east the main range is drained by the Plantain Garden river, the tributaries of which form deep ravines and narrow gorges. The valley of the Plantain Garden expands into a picturesque and fertile plain. The Black river flows through a level country, and is navigable by small craft for about 30 m. The Salt river and the Cabaritta, also in the south, are navigable by barges. Other rivers of the south are the Rio Cobre (on which are irrigation works for the sugar and fruit plantations), the Yallahs and the Rio Minho; in the north are the Martha Brae, the White river, the Great Spanish river, and the Rio Grande. Vestiges of intermittent volcanic action occur, and there are several medicinal springs. Jamaica has 16 harbours, the chief of which are Port Morant, Kingston, Old Harbour, Montego Bay, Falmouth, St Ann's Bay, Port Maria and Port Antonio.