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Its hardness is 2.75 to 3, and its specific gravity is 6.7 to 7. Its streak is white. Molybdite, or molybdic ochre, is a hydrous ferric molybdate, FeO3.3MoO3.72 H2O, and contains 39.6 per cent molybdenum. It occurs as an earthy, yellow powder, or in hair-like crystals of pale yellow color, usually associated with molybdenite, of which it is an alteration product. Alone, it is not an important ore of molybdenum. It has a dull lustre, a straw yellow streak, a hardness of 1 to 2, and a specific gravity of 4.5. Powellite is calcium molybdate, CaMoO,, and contains 48 per cent molybdenum. Sometimes tungsten replaces part of the molybdenum. It is greenish-yellow to dull gray in color, subtransparent, resinous, without cleavage, has an uneven fracture, a hardness of 3.5, and a specific gravity of 4.52. Ilsemannite is an oxide of molybdenum, MOO2.4MOO, and contains about 68 per cent molybdenum. It is a blue-black to black cryptocrystalline mineral, associated with barite and wulfenite. It is soluble in water, giving a deep blue solution which on evaporation yields dark blue crystals. Rare. Belonesite is magnesium molybdate, MgMoO, and contains 52 per cent molybdenum. It is a white transparent mineral, occurring in minute tetragonal crystals. It occurs in rock fragments enveloped in Vesuvian lava. Rare. Pateraite is cobalt molybdate, CoMoO., and contains 43.8 per cent molybdenum, or it is molybdate of cobalt and iron, FeCoMo2Os, and contains 44.1 per cent molybdenum. It is an impure massive black mineral associated with uranium minerals. Rare. Achrematite is lead arsenate, chloride and molybdate, 3(3PbaAs2O8.PbCl2)4 (Pb2MoOs), and contains 3.4 per cent molybdenum. It is a massive, cryptocrystalline mineral with an uneven to subconchoidal fracture, is brittle, has a hardness of 3 to 4, and a specific gravity of about 6. Its color is sulphur-yellow to orange and red, but in mass is liver-brown, owing to admixture of limonite. Its streak is pale cinnamon brown. Its lustre is resinous to adamantine, and fragments are translucent on thin edges. Eosite is a vanado-molybdate of lead, Pb.V.MoO16, and contains 8.9 per cent molybdenum. Its color is deep Aurora-red. It has a brownish, orange-yellow streak. Its hardness is 3 to 4. It occurs in minute octahedral crystals of the tetragonal system which are found on pyromorphite and cerrusite. Molybdurane is molybdate of uranium, UO UO3.2MOO.. Molybdoferrite is molybdate of iron, FeMOO..

MOLYBDENUM, mo-lib'dē-nům, a pure white metal, softer than steel,. malleable and capable of being forged and welded. It can be filed and polished and may be drawn into ribbons and fine wire. Metallic molybdenum is used in various electrical contact making and breaking devices, in X-ray tubes, in voltage rectifiers, in the form of wire for filament supports in incandescent electric lamps, for winding electric resistance furnaces and in dentistry. It is also employed in the manufacture of chemical reagents, dyes, glazes and disinfectants. The principal use of molybdenum is in the manufacture of special alloy steels, usually in conjunction with chromium, manganese, nickel, cobalt, tungsten or vanadium. These steels are used for self-hardening and highspeed machine tools, for crank-shaft and pro

peller-shaft forgings, high-pressure boiler pla armor-piercing projectiles, permanent mach and wire. During the World War the mi uses were for gun-linings, armor plates, pro jectiles and in the motor industry, especially r the crank-shafts and connecting-rods of Liber | motors. The purest molybdenum is produs. Į from wulfenite, but practically the whole the world's supply of the metal and its conpounds is obtained from molybdenite (qv Molybdenite resembles galena in some respec and owes its name to this fact, the won "molybdenite" being based upon the Latin nam for galena. It was first clearly distinguisher from galena by Scheele in 1778, and in 178 Hjelm obtained the element molybdenum in t metallic form, Molybdenum may be prepared by reducing the oxide by hydrogen, carbon or potassium cyanide, as well as by various othe methods. It has a specific gravity of about and a specific heat of about 0.0659. Its meking point is higher than that of platinum Molybdenum is not affected by air or moistur at ordinary temperatures, but oxidizes slowly when heated in air, and at high temperatures it burns, whether heated in air or in steam Chemically, molybdenum behaves both as a metal and as a non-metal. It has the chemica symbol Mo and an atomic weight of 9% : O=16, or 95.3 if H=1. It forms several oxides, of which the trioxide, MoOs, is the most important, This is the oxide that is formed when the metal is burned in air, and it may also be prepared by roasting the native sulphide in air. The trioxide occurs native in small quan tities, as "molybdenum ochre," or "molybdite Metallic molybdenum combines directly with chlorine to form MoCls, and with bromine t form MoBr; but it does not combine directly with iodine. Unlike the other metals, moly denum does not readily replace the hydrogen of acids to form definite salts, but its oxide dissolve in acids with the formation of com pounds which have, as yet, been but little studied. The trioxide combines with water to form substances of the nature of acids, and which are, in fact, called "molybdic acids." These further combine with metallic bases to form ar extensive series of compounds known as "molybdates." Ammonium molybdate is used in the laboratory as a reagent for the detection of phosphoric acid, a yellow precipitate being thrown down when a nitric acid solution of ammonium molybdate is added to a solution containing a phosphate. Consult Wolf, H. J. 'Molybdenum (Golden, Colo., 1918); Wilson, A. W. G., "Molybdenum" in The Mineral Industry during 1916, Vol. XXV.

MOLYNEUX, mol'i-nooks, William, Irish philosopher: b. Dublin, 17 April 1656; d. there. 11 Oct. 1698. He was graduated from Trinity College, Dublin, entered the Middle Temple, London, became a student of applied mathematics and philosophy, and a friend of Locke; was elected F. R. S. in 1685 and was elected to Parliament for Dublin University in 1692 and 1695. Besides his 'Dioptrica nova) (1692) on optics and philosophy, he wrote "The Case of Ireland's Being Bound by Acts of Parliament in England (1698), a work on the legislative independence of Ireland, which created a considerable sensation.

MOMBASA, mom-bä'sä, Africa, an island nd town on the east coast, the town, capital f the Seyidie province, the chief seaport and he seat of administration of British East Africa, being on the north side of the island, which is three miles long by two and one-half niles wide, close to the coast, 150 miles north f Zanzibar, lat. 4° 3′ S. Here are an old Portuguese fort, a new European hospital and he offices and workshops of the British East Africa Company. A short railway connects Mombasa with Kilindini, the naval coaling lepot, on the other side of the island, where is he residence of the chief administrator of the company. Mombasa is also the terminus of a ailway connecting with the Victoria Nyanza. Trade in (imports) piece-goods, brass and Iron wire, beads, rice; and in (exports) ivory, gum, copal, copra, ochella weed, maize and grain; carried on by natives of British India. Pop. about 30,000. Island and port are mentioned as early as 1331. It was visited by Vasco de Gama in 1497, held by the Portuguese from 1529 to 1698 and by the British from 1824 to 1826, but the British refused to accept cession of it. Soon after the sultan of Muscat obtained possession of the town, which at his death fell to his son, the sultan of Zanzibar. In 1888 the Imperial British East Africa Company received governing rights over it from the sultan of Zanzibar, since when it has passed definitely over to the possession of Britain, along with the huge territory on the mainland allotted to that country.

MOMENT of a dynamical quantity is the importance of that quantity in regard to its dynamical effect relatively to a given point or axis. The moment of a force about a point is the product of its amount into its perpendicular distance from the point. The tendency of the action of such a force is to cause rotation about an axis perpendicular to the plane passing through the point and containing the force. Thus, in the case of a pendulum, the effectiveness of the force in causing rotation is measured by the moment WI, where W is the weight of the pendulum, and is the distance of the line of action of the force W from the centre of rotation C, or the distance of the centre of mass G from the vertical line through C. The term moment enters into several other phrases, all of which relate either directly or indirectly to rotation. Thus, there is the moment of momentum, or angular momentum, whose rate of change is the measure of the moment of the force producing the change. To obtain it for any given body rotating with angular speed about an axis, we first imagine the body broken up into a great many small portions of masses m1, m2, ms, etc., at distances 1,2,3, etc., from the axis, multiply the momentum (mr) of each mass by its distance, and then take the sum of all these products. The angular speed w being the same in every expression, the moment of momentum takes the form w (mir+mara+, etc.), which it is usual to write in the symbolic form w mr2. quantity & mr, which is the sum of the products of each mass into the square of its distance from the axis, is called the moment of inertia about that axis. It is the factor in the moment of momentum which depends upon the distribution of matter in the body. It enters

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into all questions of mechanics in which rotation is involved, from the spinning of a top or the action of an engine governor to the stability of a ship. By an obvious extension, the word moment is also used in such combinations as moment of a velocity and moment of an acceleration. Such phrases correspond to nothing truly dynamic, unless we regard velocity as meaning the momentum of unit mass and acceleration as the rate of change of that momentum.

If the mass of every small portion of matter in a body be multiplied by the square of its perpendicular distance from a straight line, the sum of all such products is called the moment of inertia of the body about the line regarded as an axis. The radius of gyration of the body is the distance from the axis at which all the matter of the body might be concentrated without altering the moment of inertia. Thus, if 1 is the moment of inertia of the body, M its whole mass and kits radius of gyration, 1 Mk. We see that the moment of inertia of a body about a line is found by adding a great number of products of small masses and squares of distances; if the body can be defined mathematically as to shape, size and density, finding its moment of inertia is a problem of the integral calculus.

ICS.

MOMENT OF INERTIA. See MECHAN

MOMENTUM, in mechanics and physics, the product of the mass and velocity of a body. Like velocity, momentum is usually regarded as having a definite direction, as well as a definite numerical magnitude. The momentum generated by a constant force acting upon a material particle for a definite length of time is numerically equal to the product of the force by the time during which it acts, and has the same direction as the force. See MECHANICS.

MOMIERS, mo'my'à', from the French term for mummers. It was a nickname given in derision to the followers in Switzerland (1814) of the Baroness von Krüdener (q.v.), who charged the State Church with apostacy, held great conventicles and lived as æsthetics. They were led by the Geneva clergyman, H. L. Empeytaz, César Malan, L. Gaussen, Merle d'Aubigny and F. Monod. From this sect arose the Evangelical Society at Geneva (1832), the Free Evangelical Church (Eglise libre) of 1848 that, in 1883, divided and went into even severer directions. Consult Goltz, von der, 'Die reformierte Kirche Genfs in 19 ten Jahrhundert' (Basle 1864).

MOMMSEN, mom'zěn (Christian Matthias) Theodor, German epigraphist and historian: b. Garding, Schleswig, 30 Nov. 1817; d. Charlottenburg, near Berlin, Prussia, 1 Nov. 1903. He was a student of jurisprudence and philology at the University of Kiel; took his Ph.D. in 1842; published with his brother Tycho and his friend Storm a volume of verse which was scathingly condemned by the reviewers (1843); began more successfully his career as historian with the treatise De Collegiis et Sodalitiis Romanorum' (1843), commended for its thoroughness and a clarity of style new to German works of this kind; and in 1844-47 was in France and Italy under commission of

the Berlin Academy, collating manuscripts and inscriptions. On his return he edited for a short while the Schleswig-Holsteinische Zeitung, and in 1848 became professor of Roman law at Leipzig. He entered politics as an advocate of constitutional progress, was arrested for inciting to revolt, and though acquitted by the courts was deprived of his professorship. From that time he was an eager if not invariably judicious disputant in many political controversies. He was appointed to the professorship of Roman law at Zürich in 1852, at Breslau in 1854; and from 1858 until his death was professor of ancient history in the University of Berlin. In 1873 he was elected perpetual secretary of the Berlin Academy; but this post he resigned in 1895. For 10 years (1873-82) he was a Liberal member of the lower house of the Prussian parliament, where he bitterly attacked Bismarck's domestic policy. In an election speech at Charlottenburg in 1882 he characterized the Iron Chancellor's tariff measures as a "Politik von Schwindel." Such boldness could not go unrebuked, and Mommsen was brought to trial for slander. quittal by both a lower and an appeals court was one of his great triumphs. He sternly advised the Teuton, element in Austria in the struggle with the Czechs; made some caustic observations in a North American Review article on British treatment of minor nations; to the last was quite as belligerent as ever.

His ac

But he was only incidentally the politician. He was pre-eminently what Freeman called "the greatest scholar of our times, well nigh the greatest scholar of all times" (Methods of Historical Study'). He was distinguished as a epigraphist, historian, jurist, numismatist and philologian. None in the 19th century, which he almost spanned, has, as Freeman goes on to say, "taken in so wide a range of subjects, all brought with the happiest effect to bear upon and to support one another." To the educated reader at large he will probably continue to be best known for his 'Römische Geschichte' (3 vols., 1854-56; 8th ed., 1889), to the battle of Thapsus; together with Vol. V on the provinces from Cæsar to Diocletian (1885). Volume IV, on Imperial Rome, was unfinished at his death. There are English renderings by W. P. Dickson (Vols. I-III 1862-66; Vol. V 1886). This work opened a new epoch in historiography. Though written with great spontaneity, without even references to original sources, it was based on unrivaled knowledge, and presented its material with extraordinary clearness and at times with brilliancy. It is of course somewhat dogmatic, is certainly unfair to Cicero, and has been blamed, by Freeman among several, for undue glorification of mere power and success. To scholars Mommsen is above all the editor of the great 'Corpus Inscriptionum Latinarum' (1863 et seq.; Vols. I, III, VIII, IX, by himself; others under his immediate supervision). Every inscription of this monumental collec tion was taken down from the original. The errors and falsities of predecessors were cleared away, and a scientific foundation was supplied for the study of Roman antiquities. Mommsen's preface to the series is said to be thought by critics one of the finest specimens of Latin prose written in modern times. For a complete list of his writings, Zangemeister's 'Mommsen als Schriftsteller' (Heidelberg

1887; new edition by Jacobs, with additions, 1905) should be consulted. Mention may be made of Römisches Münzwesen) (1850), 'Römische Chronologie) (1859) and ‘Römisches Staatsrecht (1871-88). All are standard, but the last, particularly, by the breadth and completeness of his exposition of the Roman constitution, places Mommsen among the foremost of constitutional writers. He also edited the 'Res Gestæ Divi Augusti ex Monumentis Ancyrano et Apolliensi (1865; new ed. 1883); the 'Digesta in Vol. I of the Corpus Juris Civilis (6th ed., 1893), and many other publications. His library, when partially burned in 1880, was replenished by gifts from foreign scholars. In 1902 he was awarded the Nobel prize in literature. Consult Hirschfeld, O., "Gedächtnisrede auf Theodor Mommsen' (1904); Sandys, J. E., A History of Classical Scholarship (Vol. III, Cambridge 1908); Wachsmuth, C., Worte zum Gedächtniss an Theodor Mommsen' (Leipzig 1904).

MOMORDICA, a genus of plants of the gourd family, remarkable for their strangely marked seeds. Two or three species are cultivated in the United States as ornamental plants, one of which (M. charantia) produces a food for the Chinese in the pulp about the sculptured seeds; another Oriental food, the golkokra of India, is the fruit of M. cochinchinensis; and the balsam-apple (M. balsamina) furnishes a healing principle which is infused in oil to form a liniment highly esteemed in the Levant.

MOMOTOMBO, mō-mō-tōm′bō, Nicaragua, an active volcano rising 4,250 feet from the northwestern shore of Lake Managua. Eruptions took place in 1852, 1902 and 1905. The nearby village of Momotombo is connected by rail with Chinandega.

MOMPOS, mōm-pos', Colombia, a town of the province of Bolivar on an island formed by the Rio Magdalena about 180 miles south of the deltaic mouth. The streets, which extend parallel to the river, are well laid out, but the houses are badly built. Mompos is a depot of foreign goods destined for consumption in the valley of the Magdalena; but the changes in the river's course rendering it unnavigable have seriously injured its prosperity. Pop. 11,000.

MOMUS, in Greek mythology, the god of satire and mirth. He is generally represented raising a mask from his face and holding a small figure in his hand. His mother was Nyx, the goddess of night. As a mocking censor and carping critic Jupiter cast him out of heaven.

MONA, mō'ną (1) a West Indian islet belonging to the United States since 1898. It lies 42 miles east of Porto Rico, in the middle of Mona Passage, to which it gives its name; seven miles long by two miles broad, its area is nearly 10,000 acres. It is of coral formation, with a general level about 60 feet above the sea. A range of hills on the east side of the island runs from north to south, the highest peak of which is 175 feet above the water. The island is well watered and well drained, has a luxuriant vegetation and all kinds of tropical fruits grow in profusion. It is the

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Showing the New Oceanographic Museum at the Tip of the Mainland

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