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LEFT FLOYD 160 FLUTE and to a systematic course of philan- thropy. He died in Eastport, Long Is- land, N. Y., May 12, 1899. FLOYD, JOHN BUCHANAN, an American statesman; born in Blacks- burg, Va., June 1, 1807; was admitted to the bar in 1828; served in the Vir- ginia Legislature several terans; and was governor of the State in 1850-1853. In 1857 President Buchanan appointed him Secretary of War. While in the cabinet he was detected in the act of stripping the Northern arsenals of arms and ammunition, and indicted by the grand jury of the District of Columbia as being privy to the abstracting of $870,000 in bonds from the Department of the Interior. He fled, however, to Vir- ginia, where, at the close of 1860, he was commissioned a general in the Confed- erate army. In that capacity he was driven from West Virginia by General Rosecrans. The night before the sur- render of Fort Donelson he stole away in the darkness, throwing the responsi- bility of surrendering on a subordinate officer, and, being censured by the Con- federate government, never afterward served in the army. He died near Ab- ingdon, Va., Aug. 26, 1863. FLUID, having the parts easily separable; consisting of particles which move and change their relative positions very readily; capable of flowing; liquid; gaseous. The fundamental property of fluids, viewed as forces, in physics, is their equality of pressure in all direc- tions. The term includes both liquids and gases. Elastic fluids: In physics, gases. Electric or electrical fluid: In electricity, a fluid composed, in the opin- ion of Symmer, now generally accepted, of two fluids, the positive and the nega- tive. Imponderable fluids: In physics, a name sometimes given to heat, light, magnetism, and electricity. They are mobHe and yet, if consisting of matter, are in such a state of tenuity that they possess no perceptible weight. Mag- netic fluids: In magnetism, two fluids as- sumed to exist. They are called respec- tively the N, or boreal fluid and the S. or austral fluid, the former predominat- ing at the N. and the latter at the S. pole of the magnet. Sometimes the N. fluid is called the positive, and the S. fluid the negative one. Ponderable fluids: In physics, those possessed of weight; as water and carbonic acid gas. FLUORESCEIN, C^Ha^Os. An im- portant dye-stuff, occurring as dark-red crusts, almost insoluble in water, but readily soluble in alkalies r.nd in alco- hol. Its alkaline solutions are dark red- dish-brown in color, and when diluted show a remarkable yellowish-green fluo- rescence, to which the material owes its name. It is prepared by heating to- gether phthalic anhydride and resorci- nol. As a dye, fluorescein has only a limited application, as the yellow color which it produces on wool and silk is not permanent. It is used largely, how- ever, in admixture with other dyes to produce fluorescence in the dyed mate- rial. The important dye Eosin is made from fluorescein. FLUORESCENCE, in optics, a quality which exists in the rays of light by which, in certain circumstances, they undergo a change of refrangibility. Hence, certain solutions which, when viewed by transmitted light, are color- less, become bluish under reflected light. Fluorescence was discovered by Stokes in 1852. FLUORINE. A very pale yellow gas, atomic weight 19, molecular weight 38, density (compared to air = 1) 1.31. It does not occur in the free state, but its compounds (fluorides) are found in abundance; the best known being fluor- spar and chrysolite. It is considered to be the most active of the elements. It decomposes water with formation of hydrofluoric acid, oxygen and ozone; all metals are attacked by the gas, some taking fire in it, spontaneously, and many other elements combine with it with incandescence. It is prepared by the electrolysis of a solution of potas- sium fluoride in anhydrous hydrofluoric acid, hydrogen being evolved at the kath- ode and fluorine at the anode. FLUOROSCOPE, a device invented by T. A. Edison for use in making observa- tions of the influence of the X-rays. FLUTE, in music, a popular instru- ment, the use of wiiich, under various forms, may be traced to the most remote ages. Of its origin no direct account can be given. In its primitive state the flute was played like the modern flageolet, with a mouth-piece at the upper end ; and from the shape of this mouth-piece, which resembled the beak of a bird, it received the name of flute a bee. In this form, with slight alterations, it continued until the beginning of the 18th century, when it was gradually superseded by the flauto traverso, or transverse flute, so called from its being blown at the side, and con- sequently held in a horizontal position. At its introduction this instrument was about 18 inches in length, and had but one key. Shortly after, a movable head- joint was invented, its lengfth being in- creased, and more keys added, some flutes at the present time having more than a dozen keys, and a few less than