Aztecs. Race of N. American Indians, who came from California or Arizona and invaded Mexico in the 12th century. 500 years before. At the time of the conquest by Cortez, it is They found the Toltecs in possession, who had preceded them probable their numbers did not exceed 250,000. They had the gens system common to the American Indians, but with certain changes; the sons inherited property, and the descent passed in the male line. The government was a military democracy; cotton was cultivated; the sun-dial was in use; and a calendar, nearly perfect, had been invented. The god of war received the chief worship; 20,000 human sacrifices were offered annually. The best houses were not over two stories, and were built of adobe, stone and gypsum.

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Azuline, or AZURINE. C,,H,,N,Cl. Impure hydrochloride of triphenylpararosaniline; prepared by the action of aniline upon rosolic acid; blue coloring matter.

Azurite. Cu,C2O+H2O. Blue hydrous copper carbonate, valuable as a copper ore when found in sufficient abundance; Chessy copper. Also iron and aluminium phosphate, more generally known as Lazulite.

Azygobranchia. Division of Gastropoda, including the Heteropods (Natantia) and Prosobranchs (Reptantia). This division of the Streptoneura includes forms that have lost their original left-side gill and excretory duct, and have the osphradium of the original right side (now on the left) developed into a parabranchia.

Azygos (AZYGOUS). Unpaired, single, or median, as the dorsal, ventral, and caudal fins of fishes; organs occurring in a sagittal plane. Also structures, or organs, on one side of the body, whose platytrope has been suppressed.

Azygosperms. Zygosperms produced by parthenogenesis in certain of the Mucorini.

Azygospore. Spore resembling a zygospore, but produced asexually.

Baader, BENEDICT FRANZ XAVER VON, 1765-1841. German theologian, prof. Univ. Munich from 1826; follower of Jakob Boehme.

Baal. Phoenician and Canaanite personification of the planet Jupiter, or the Sun, whose worship, with that of the goddess Ashtoreth, was the great corrupter of pre-exilic Israel. Baalbek. Site of the ancient Heliopolis in Syria, between the Lebanon and Anti-Lebanon mountains, and a day's journey n. of the road from Beyrout to Damascus. Here are the most

Ruins of the Great Temple at Baalbek, with the Lebanon Range. imposing Roman temple ruins in existence, dating from the Antonines-a temple of Jupiter and one of the Sun. The acropolis on which these buildings stood has foundations of enormous stone blocks dating from the Phoenician period. Three of them are each 64 ft. long, 15 ft. high, 15 ft. thick, and weigh about 1,100 tons each.

Babbage, CHARLES, F.R.S., 1790-1871. English mathematician, Cambridge_1828-39, inventor of a calculating machine, not completed. Economy of Manufactures, 1832; Calculus of Functions.

Babbitt-Metal. Alloy for lining moving surfaces in machinery which are exposed to friction of motion under pressure. Usual proportions, 91 per cent tin, 7 of antimony, and 2 of copper. It has a low coefficient of friction, a high conductivity for heat, is easily fusible, and expands on cooling so that it can be melted and poured into a bearing when renewal is

necessary

Babcock, STEPHEN MOULTON, b. 1843. American agricultural chemist, prof. Univ. Wisconsin. He has given particular attention to the chemistry of milk, and is the inventor of the Babcock Milk Test for the rapid determination of fat in milk.

Babcock's Milk Test. Pub. 1890. 17.5 C.C. milk are mixed with same quantity of sulphuric acid, 1.82 Sp. G., in test bottle with graduated neck. The albuminoids, casein, are changed to soluble albumens. The bottles are whirled in a horizontal wheel for several minutes at 200° F. The wheel has a hot water jacket. The bottles are then filled to the neck with hot water and whirled two minutes longer. The fat is read liquid at 150° F.

Babel. Tower attempted to be built after the Flood; Gen. xi. Also Nimrod's city, Babylon; Gen. x. 10.

Bab-el-Mandeb. Strait connecting Red Sea with Indian

who conspired to overthrow the Directory and establish a communistic republic, but was guillotined. His doctrines were revived 1828, and became an element of the later socialism.

Its

Babi, or BABISTS. Persian sect; founded ab. 1844, by Mirza Ali (d. 1850); partially suppressed 1852, but still numerous. members urge certain humane reforms, and venerate their founder, the Bab, as above Mohammed.

Paris, author of many papers on meteorological subjects. Babinet, JACQUES, 1794-1872. Prof. physics at Poitiers and

Babinet's, or JAMIN'S, Compensator. Apparatus for studying elliptically-polarized light. Two wedges of quartz of the same small angle are cut with one face of each wedge parallel to the optic axis, which in one is parallel to the edge, in the other at right angles to the edge. The two are put together so as to form a plate, the angles of the wedges being turned in opposite directions, while the optic axis in both crystals is parallel to the faces of the plates.

Babington, WILLIAM, 1756-1833. British chemist and mineralogist. New System of Mineralogy, 1799.

Baboons. Dog-faced monkeys (Cynocephalus), living in troops in inaccessible or rocky heights, but descending daily to drink. They live on fruits and grubs, and defend themselves by throwing stones. The ordinary Baboon of n. Africa has a long tail, as has a species from the Cape of Good Hope, but the Drill or Mandrill of w. Africa has a stumpy tail, and peculiarly

Babrius. Greek fabulist of uncertain date A.D. His poems came to light 1843-44.

Babuyan. Volcanic islands n. of the Philippines, held by Spain.

Babylas, ST. Bp. of Antioch 237, martyred 250. His bones troubled the adjacent heathen worship, and were removed to Italy in the Middle Ages.

Babylon. Ancient city on both sides of Euphrates, in form

of a square, 14 m. on each side, according to Herodotus; 103 m. according to Ctesias. It was inclosed by two walls 300 ft. high and 85 wide, outside of which was a deep moat. The walls were pierced on each side by 25 gates of brass, as also were the walls on either bank of the river. The buildings were of brick, burned or sun-dried. Its most famous structures were the Temple of Bel, 8 stages high, rising from a base 600 ft. square, and the Hanging Gardens, raised upon a series of arches ab. 75 ft. high. The Assyrians captured B. in 14th century B.C., and established a Semitic dynasty here, which continued till the accession of Nabonassar 747; Assyrians again gained supremacy 680, and retained it till fall of Ninevah 625, when Nabopolassar secured its independence. Nebuchadnezzar reigned 604-561, and built the walls, hanging gardens, and other massive structures; conquered Syria, Judea, Egypt: destroyed temple at Jerusalem 587. Cyrus took B. by stratagem 538; Alexander took it 331, and intended it for his capital, but died here 323. Seat of government transferred to Seleucia ab. 300. Long the center of Asiatic material civilization, her luxury, idolatry, and oppression called forth from Hebrew prophets threats of the desolation which has for many centuries been her fate. The name was by analogy used by St. John and St. Peter for Rome.

Babylonia. Lower portion of the region between the Tigris and Euphrates. Its early history, as given by Berosus and Herodotus, claims great antiquity. Its chief city was Babylon; it waged war with the Assyrians to the north, with varying success. Tiglath Pileser, the founder of the second Assyrian empire, conquered B. 744 B.C. It was under Assyrian sway until the revolt of Nabopolassar 625. His son Nebuchadnezzar (604-561) was master of a great empire. This was overthrown later on by the Persians under Cyrus, who merged it in his empire. Remains unearthed show that the arts had reached considerable development. The cuneiform inscriptions upon brick cylinders are being rapidly deciphered, and give much information regarding the religion, mythology, daily life and history of the Babylonians. Americans are actively interested in this work, and Univ. Pa. has sent two expeditions to explore its ruins.

Babylonian Architecture. Brought to light by the researches of Layard and Rawlinson. It strongly resembles Assyrian in the plans and purposes of the buildings. The main difference is that no stone was used in these, which are entirely of clay, either sun-dried or burned in kilns, and for decorative purposes enameled with colored glazes. The principal buildings of which the ruins have been found and explored are the Kasr, built of brick, bearing the stamp of Nebuchadnezzar, ab. 600 B.C., on an artificial mound on the e. bank of the Euphrates; and the Birs Nimroud, a pyramid in six receding stories or terraces, averaging nearly 20 ft. in height, and in plan a square of some 280 ft. at the base; supposed to have been the chief temple of Chaldean worship.

Babylonian Captivity (SO-CALLED) OF THE CHURCH, 1305-1377, when Rome was deprived of her Pontiff, the Popes residing at Avignon.

Babyroussa. Horned hog; found in Java, Borneo, and Molucca Is.

Baccalaureate. Graduate or bachelor of arts; also sermon before college commencement.

Baccarat. French game of cards, played upon an oval table, with 12 marked divisions, 6 on each side of the banker, opposite to whom is an assistant or croupier. The bank is sold by auction to the highest bidder. The players draw for places, the lowest sitting at the right of the banker and so on. Three packs of cards are shuffled together and cut. Each player places his bet in front of him. The first players on the right and left of the banker play for their respective sides until they lose, when the two next follow until they lose, and so on. The banker deals a card to the right hand player, then to the left, and then to himself, and then repeats the deal. The object is to make 9, the court cards and tens are Baccarat or zero and are not counted, and also 10 in the score, thus if the two cards count 12 it is called 2. If the player has 4 or less in the two cards he must take another card, if he has 6 or more, he must decline a card. If he violates the rule, he must pay all the bets of his side of the table. If the two cards add up 8 or 9 it must be declared. Only one card can be drawn in addition to the first two. The banker pays or is paid according to the hands; in case the hand is equal to his own, neither the player nor himself wins.

Bacchanalia. Feasts of Bacchus, celebrated by night with great disorder and licentiousness; forbidden at Rome 186 B.C.

Bacchus. Son of Jupiter and Semele, the daughter of Cadmus; god of wine. After his return from an expedition to India, he instituted at Thebes festivals for women, which gradually became more wild and dissolute. He is represented as a voluptuous youth, with a form approaching the feminine. Bacchylides, OF KEOS. Greek lyric poet of 5th century B.C., a rival of Pindar.

Bach, JOHANN SEBASTIAN, 16851750. German composer, most eminent of a family long noted as musicians; organist at Arnstadt, Mühlhausen, and Weimar 1703-15; Chapel

master at the court of Anhalt-Cöthen

1716-22. In 1723 he went to Leipsic and became Cantor of the St. Thomas School and director of the music in four churches. He was unequalled as an organ and clavichord player, a master of the technical part of violin playing, knew thoroughly the structure of the organ, invented an instrument midway between the violoncello and viola, called viola pomposa, combined the lute and cembalo in a keyed instrument, and invented a system of tuning the clavier with equal temperament. He was the greatest of all fugue writers and the father of the modern art. His chief works are the Mass in B minor; Passion according to St. Matthew; The Organ Fugues; and Well-Tempered Clavichord.-Of his sons, WILHELM FRIEDEMANN, 1710-1784, was the leading organist of his time; KARL PHILIPP EMANUEL, 1714-1788, was a composer, author of a book on the piano, and court musician to Frederick II. of Prussia 1740-67; JOHANN CHRISTIAN, 1735-1782, was organist in Milan and later in London.

Bacchus.

Bache, ALEXANDER DALLAS, LL.D., 1806-1867. Great grandson of Benjamin Franklin; prof. Univ. Pa. 1828; pres. Girard College 1836, where he established a magnetic and meteorological observatory; superintendent U. S. Coast Survey from 1843; first pres. National Academy of Sciences 1863. Magnetic Observations made at Girard College, 3 vols., 1840-47; Lectures on Switzerland, 1870.

Bachelor's Buttons. Double-flowered forms of Buttercups, often planted for ornament. Also Centaurea nigra, a weed of the Composite family.

Bachet, CLAUD GASPARD, 1581-1638. French mathematician. First to solve indeterminate equations by continued fractions. Problèmes Plaisants, 1612.

Bachman, JOHN, D.D.,LL.D., 1790-1874. American naturalist. He co-operated with Audubon, especially in the Quadrupeds of North America, 1846-50.

Bacillariaceæ. See DIATOMACEÆ.
Bacilli. See MICRO-ORGANISMS.

Bacillus. Genus of rod-shaped BACTERIA (q.v.).

Bacillus tuberculosis. Germ whose diameter is about of an inch and whose length varies up to ab. 000 of an inch. It breeds in the tissues of warm-blooded animals, and there produces tubercles that gradually break up and pass their germ contents into the blood, so that the disease often becomes transported to other organs. When the tubercle breaks into an air passage in the lungs, the germs are coughed up, and when dried are taken up by the air as dust, and so may infect other animals or man. The diagnosis of this germ by microscopic examination is usually difficult, especially when present in milk, unless so abundant as to average one germ per drop. To prove its presence it is needful to subject the sample (of sputum from a consumptive, e.g., first dried on a glass slide and heated), to a prolonged action of a powerful aniline dye, like fuchsin or gentian violet, at ordinary temperatures, and at 212° F. a few minutes may suffice. Then the slide must be washed in 30 per cent nitric acid until apparently decolorized. This takes the color out of ordinary bacteria, but not out of the tubercle germ. Washing in water follows, and usually a staining with a complementary color of the other objects on the slide is practiced, to help in seeing the germs. A magnifying power of over 600 diameters is needed to see them satisfactorily.

Back, SIR GEORGE, 1796-1878. English navigator, who sailed with Sir John Franklin 1819, and in 1833 led an expedition in search of Capt. Ross.

Back-acting Engine. One in which the cross-head and the main shaft of the engine are at opposite ends of the steamcylinder, or in which the connecting-rod or rods are carried backward from the cross-head instead of forward to connect the latter to the crank or beam-pin. Such engines are designed to secure compactness, as the length of the connecting-rod (over four cranks in length), is subtracted from the sum of the lengths of the cylinder-casting and of the piston-rod (which will be over twice the stroke), instead of being added to that sum, to get the entire length of the mechanism.

Back-connection. In a marine boiler, or in the setting of an externally-fired return stationary boiler, the part of the flue-passages in which the smoke or hot gases pass upward from the combustion-chamber behind the grate or fire-box, in order to come forward through the tubes or flues in the waterspace to the front end of the boiler. The English call it the back uptake."

Backergunge, or BAKARGANJ. A fertile district of 3,649 sq. m., pop. 1,900,889, on lower Ganges and Bramapootra, India, n. of the Sunderbunds.

Backgammon. Said to have been invented in 10th century. Game played by two persons with pieces on a board with 24 divisions according to the throws with two dice. Two principal games are played in Europe and America, one in which the pieces, 15 on each side, are set on certain points on the board at the commencement of the game, and the other, called Russian or Trictrac, in which they are not thus set, but each

player enters his pieces at the beginning at the same table and moves in the same direction. The game is common in China under the name of shéung luk, "double sixes" (in Japanese, sugoroko), and is played in Siam under the name of saka, with a little tower into which the dice are thrown in the manner described by Greek and Latin authors.

Back-Gear. In an engine-lathe for metal turning or in a drill or milling machine, a short shaft parallel to the spindle which carries the nest of cone-pulleys. On this short shaft are two or three toothed wheels. The cone-pulley casting which carries the belt has cast or fastened to it a small gear which engages with a large gear on the back-gear shaft. The conepulley casting turns freely on the spindle. At the other end of the back-gear shaft is a small gear which engages with a large gear keyed on the spindle of the tool, so that the driving speed and power of the belt is carried round the nest of conepulleys back to its axis again with great reduction in speed and increase of power. The usual ratio of gain is as 1:10 or as 1:16. In lathes which are triple-geared there is a third wheel on the back-gear shaft, so that at will the spindle may be driven by the former gear, or the face-plate or chuck-plate may be driven from teeth on its periphery, by this third wheel. See LATHE.

Backhuisen, or BAKHUYSEN, LUDOLF, 1631-1700. Dutch marine painter.

Backing. Rubble masonry used in the middle part of a pier or at the back of a wall, consisting of small rough stones. Back Stay. Rods or chains which run from the top of a tower of a suspension bridge backward to an anchorage.

Backus, ISAAC, 1724-1806. Historian of the Baptists in New England, 1777-96.

Backwater. Rise of water in a stream, due to construction of a dam, or to obstruction by piers. In such case the water surface at points several miles up stream from the dam is

often much elevated. The curve of this backwater has been investigated by hydraulic engineers, and tables have been constructed for facilitating computations.

Bacon, FRANCIS, 1561-1626. English lawyer and philosopher, son of Sir Nicholas (1509-1579), Keeper of the Seal. He climbed slowly under the patronage of Lord Burghley and the Earl of Essex; M.P. 1584. Under James I. he became Attorney-General 1613, Privy Councilor 1616, Lord Chancellor 1618, Baron Verulam 1618, Viscount St. Albans 1621; convicted of bribery and removed from office 1621; celebrated for his Essays, completed 1612; Apothegms, History of Henry VII., and several miscellaneous works. His chief fame rests upon his philosophical treatises, which show him to be one of the greatest thinkers that ever lived. He endeavored to refound the study of science upon the basis of inductive reasoning, thus becoming the forerunner of modern investigation. This portion of his works is classified under the heads of the Instaurstio Magna, which were: Partitiones Scientiarum, a survey of science; Interpretatio Nature, or the new method represented in the Novum Organum; Historia Naturalis et Experimentalis, a lectus, types of study; Prodromi, a training for The New Phicollection of facts for use in applying the method; Scala Intellosophy; Works, 7 vols., 1870.

Bacon, LEONARD, D.D., LL.D., 1802-1881. Pastor in New Haven from 1825. Genesis of the New England Churches, 1874. that B. wrote Shakespeare's plays. (Putnam's Mag. 1856.) -His sister, DELIA, 1811-1859, originated and urged the theory

Bacon, ROGER, ab.1214-1294. English Franciscan of genius and rare scientific attainments, who endured much persecution and was in prison as a magician from ab. 1278; so far beyond his age that his memory has been encumbered with legends, and he appears a figure of romance rather than reality. He devoted much attention to physics and chemistry. His Opus Majus, ab. 1266, was pub. 1733, and some of his treatises 1859.

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Bacon's Rebellion. Uprising in Virginia 1676 under the lead of Nathaniel Bacon, a planter, who asked permission to take measures for defense against the Indians, whose movements seemed to threaten the extermination of the whites. Though this was not granted, he gathered his forces and won two signal victories, one of them at Bloody Run," in the present bounds of Richmond. Bacon extorted from Gov. Berkeley a major's commission, a letter to the king exculpating himself and followers, the repeal of some statutes, and the enactment of others. As Berkeley soon reversed this action, and proceeded against Bacon as a rebel, Bacon captured and burned Jamestown, the governor taking to his fleet. Bacon's career was cut short by his death Oct. 29, 1676. His motives seem to have been pure and patriotic, and his rebellion to have had abundant justification in the condition of the colony. After his death the people still sought the re-enactment of Bacon's laws."

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Different Kinds of Bacteria (mostly after Koch):

A, Micr cocci, in drinking-water; B. in splenic fever; C, in cholera (Koch); D, from surface of water; E, in splenic fever (in thread-form, and with incipient spores); F. Spirillum, from putrefaction; G, Spirochete, from the teeth; H, in relapsing fever, from blood; 1, different forms of cholera inicrobe (Koch).

curved or spiral in shape, and multiply by growing in the direction of the longer axis and then breaking into two equal parts; some also reproduce by spores. Some can swim actively