from 35 to 40 feet in height, with 30 towers, and a castle with a Turkish garrison, making it one of the strongest fortified places in that part of Arabia. The present population (about 46,000), live by agriculture and the alms or spoils of the pilgrims who flock thither, as to Mecca, but at no particular time. The prophet's mosque is thought to be built on the spot where Mohammed died and to surround his tomb. The sepulcher is an irregular chamber, 50 to 55 feet in height, with a large, gilt crescent above. Within, costly curtains, embroidered with gilt letters, cover a square building of black marble, where the prophet's body is believed to lie, undecayed, with the face toward Mecca. No European has ever been allowed to see the coffin, which is cased with silver and covered with a marble slab; but there seems no reason to doubt that it really is the burial-place of Mohammed. The city once was famed for its scholars and theologians, and in the 7th century was the capital of Islam. On Sept. 1, 1908, the Medina and Damascus railway, 1,000 miles long, w..s opened to traffic.

Medieval Period. See Geology.

Med'iterra'nean, The, is the laregst inclosed sea. It is connected with the open ocean (the Atlantic) only by the narrow Strait of Gibraltar, nine miles wide. The name is derived from its being in the midst of three continents : Europe, Asia and Africa. It is 2,200 miles long, varies from 500 to 100 miles in width, and has an area of 900,000 square miles. I'" is connected with the Black Sea by the Dardanelles, Sea of Marmora and the Bosporus. The coasts of Europe and Asia Minor have many bays and gulfs, while the coast of Africa is even, with few indentations. The Tyrrhenian Ionian, Iberian and gean Seas and the Levant are different parts of the Mediterranean. Sardinia, Corsica, Sicily, Malta, Cyprus and Crete are among the larger islands. The region is subject to earthquakes, and Vesuvius, Stromboli and tna are its most famous volcanoes. The bottom is divided into two parts by a ridge which crosses it from Sicily to Africa, the water being deeper in the eastern basin. The evaporation is greater than the amount of water poured into the Mediterranean by its rivers, and if it were not for the water of the Atlantic which flows in at Gibraltar, above the outflow of the heavier water of the Mediterranean, the sea would become Salter and shrink into two salt-lakes like the Dead Sea. Suez Canal connects the Mediterranean with the Red Sea. The chief rivers that flow into it are the Rhne, Po and Nile. The ountries bordering the Mediterranean (Phoenicia, Greece, Egypt and Italy) have been cradles of civilization, and the sea is well-known in history, poetry and ancient story, and to-day is one of the most important water-routes of the world.

Medulla Oblongata {m-dil'lă ŏb-lon-ga'ta), the part of the hind-brain merging into the spinal cord, the hind-brain being made of the cerebellum and the medulla oblongata. It is a very important part of the brain. The cranial nerves, with the exception of the optic and olfactory nerves, are connected with it, and in it are also located clusters of nerve-cells — or especial centers,— that preside over special actions. Here, for example, are located the respiratory center, controlling the respiratory movements; the cardiac center, for regulating the action of the heart; the vasomotor center, for regulating the calibre of the blood vessels; the sneezing center; and others. These centers may be excited to greater activity or held in check (inhibited) by various forms of stimulation from the external world or from within the body. See Brain.

Medusa (m-dū's), in Greek mythology, one of three sisters called the Gorgons. They had but one eye among them, a fortunate circumstance, as whoever they looked on was changed to stone. Medusa is represented in art as a winged virgin, with hissing snakes for hair, brazen claws and a single tusk for a tooth. They kept the garden of the Hesperides, where Medusa was slain by Perseus.

Medusae (m-dū'sĕ), a group of free-swimming jellyfish. They have a dome-shaped or umbrella-shaped swimming-disc of jellylike consistency. From the margin of the disc hang many tentacles, which, from their fancied resemblance to the snaky locks of Medusa the gorgon, gave these animals their name. See Cœlenterata, Hydrozoa and Jellyfish.

Meerschaum (mr'sham), is a mineral, found in several parts of the world, consisting of hydrous magnesium silicate. It is a white, clay-like substance, which, when dry, will float on water: hence its name, which means sea-foam. When first dug from the earth it is soft, like soap, makes a lather in water and takes out grease, and is often used instead of soap by the Turks. In Europe it is found in Moravia, Spain and the Crimea, and in Turkey in Asia there are large beds of it just below the soil. It is also found in South Carolina. It is used almost entirely for the manufacture of tobacco-pipes, the Austrians being the most largely engaged in the trade. The pipes made at Vienna often are worth $500, from the great beauty of their design. The waste material left after cutting the pipes is ground into powder and mixed into a paste, from which the cheaper pipes are made.

Megaphone (mĕg'-fōn), a large funnel-shaped tube used for reflecting sound. A tube of this kind may be used either to receive sound, when it becomes an ear-trumpet, or it may be used to transmit sound, in which case it becomes a speaking-