MIRAGE                                                      1239                               MISSIONARY RIDGE

Mirage (m'rzh') is an appearance of an object in the sky or at sea above the water, produced by the rays of light changing their direction when they pass through a layer of hotter or of colder air. The mirage of the desert is the effect of the heating of the layer of air next the ground by the hot sands, thus bending the rays of light upward; while over water the effect is produced by the rays of light being bent as they pass from the cool layer of air next the water into hotter air above. Sometimes the object is seen in the sky upside down, occasionally only slightly raised, and sometimes there will be two objects, one upright and the other reversed. These effects are all explained by the different layers of hot and cold air through which the light passes. There have been some very remarkable mirages; as the Fata Morgana in the Straits of Messina, where men, houses and ships are seen, sometimes in the water and sometimes in the air. Captain Scoresby, while cruising off the coast of Greenland, discovered his father's ship by its image or reflection in the sky. On the Baltic, in 1854, the English fleet of 19 vessels, 30 miles away, was distinctly seen floating in the air. See Optics by Brewster.

Miramon (mē'r-mn'), Miguel, a Mexican general, was born in the City of Mexico, Sept. 29, 1832. "While still in the military academy, he, with his fellow students, engaged in defending Chapultepec in the war with the United States, and he was taken prisoner. Entering the army in 1852, he became colonel in 1855 and general when 25. When in command of a body of troops, he headed a rebellion against Alvarez, the president of the country at the time, and took the city of Pueblo, which he twice defended within six months, the second time for 43 days against 10,000 besiegers. He kept up his opposition to the government, as the head of the church party, and was finally chosen president in 1859, but declined the honor, reinstating Zuloaga, who retired in a few days, leaving Miramoi in command. The war continued until i860, when the Liberal party gained power and Miramon fled to Europe. Maximilian, to whose fortunes he adhered, made him grand-marshal and minister of Mexico to Berlin. He returned to Mexico in i860, when Maximilian was reigning, and the latter persuaded him to give up his intention of resigning. As chief of the army he was captured and shot at Quertaro, with Maximilian, June 19, 1867. See Mexico under Maximilian by Kendall ; Young Folks' History of Mexico by Ober; and Mexico and Her Military Chieftains by Robinson.

Miramichi (mr'-m-shēr), a river in New Brunswick, flows into the Gulf of St. Lawrence about midway up the eastern coast, creating a large indentation. Near ■ its

mouth lie Newcastle and Chatham, and there is a fine harbor between them. West of Newcastle the Miramichi is divided in a great spray of branches which drain the middle of New Brunswick, and make its greatest lumber river, next to the St. John.

Mir'ror, a surface capable of reflecting light. Ancient mirrors, now found in tombs and sepulchral vaults, were for the most part made of solid, highly-polished metal; but upon the use of glass becoming common, that material took the place of heavier substances. The backs of the first glass mirrors were covered with a thin coating of lead, but the glass workers of Venice in the 17th century introduced an amalgam of mercury and tin which answered the purpose much better. A solid and perfectly level table of stone is first covered with a sheet of tin-foil, over which a quantity of mercury is poured,raised edges preventing the loss of it. Upon this liquid mercury a carefully-prepared plate of glass is slid in such manner as to exclude air-bubbles and impurities. The superfluous liquid is then run off, and by means of delicate and uniform pressure the amalgam is made to adhere to the glass. The plate, being lifted from its position, is turned with the coated side uppermost to dry. This process sometimes requires weeks.

Missionary Ridge. The battle of Missionary Ridge was fought Nov. 24 and 25, 1863, by the Union forces under Grant and the Confederates under Bragg. The latter occupied Lookout Mountain and Missionary Ridge, and the valley between, four miles wide. Hooker in command of Grant's right stormed and carried Lookout Mountain on the 24th, the Confederate lines being withdrawn to Missionary Ridge. On the same day Sherman crossed the Tennessee and on the morning of the 25 th moved against Bragg's right which held the northern base of Missionary Ridge. Desperate fighting ensued, the Confederate lines being stubbornly held against Sherman's repeated assaults. In the afternoon Grant, who watched the struggle from Orchard Knob, ordered his entire center forward to attack the Confederate earthworks at the western base of the ridge. The four divisions forming the lines were from left to right Baird, Wood, Sheridan and Johnson, and they faced the ridge at distances from three quarters of a mile to a mile. At a signal the whole line charged under fire of 100 guns from the crest and in face of a rifle-fire from the entrenchments at the base.* The entire line was taken, the Federal lines were quickly reformed, and without orders charged up the face of the ridge. The whole line gained the crest near together, and after a short struggle carried three miles of the crest, and captured 37 guns and about 2,000 prisoners.