Aquatint

pondweed (Aponogeton) and Canadian pondweed (Elodea) are other examples; but there are many more. The majority of water plants are fixed in the soil, but some, like duckweed (Lemna) and water soldier (Stratiotes), float, or at least are free from the soil. The whole surface of a water plant in contact with the water absorbs liquid and gaseous food, and, in the case of flowering plants, such absorptive surfaces are almost or entirely devoid of the stomata and cuticle which are commonly found in the epidermal surfaces of land plants; but both stomata and cuticle occur on the

Water-Soldier.

upper surfaces of floating leaves. The vascular and fibrous tissues of the stems and leaves are poorly developed, since they are scarcely required, and the roots are reduced. Large air-spaces occur in the cellular tissue of most water plants, and these become filled with oxygen, for the better respiration of the plant. Most aquatic plants expose their flowers above the surface, and thus are subject to the same means of pollination as land plants. A few only have entirely submerged flowers, as in sea wrack (Zostera), which, like very few other plants, is submerged in sea water. Most aquatic plants are perennial. Some-e.g. Utricularia (see BLADDERWORT)-form dense terminal winter buds in autumn: these drop off, rest at the bottom during the winter, and then develop during the following spring. Others perennate by means of fleshy rhizomes, which store up food.

Aquatint, an etching process on copper by which prints are produced imitating the broad effects of India ink and sepia drawings. In this process, areas, not lines, are bitten in by dilute acid on a copper plate, covered with black resin, on which the design has already been traced. Devised by Abbé St. Non in the 18th century, and perfected by Jean Baptiste le Prince (1733-81), the process has now fallen into disuse, except for

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the tints printed in some colored pictures.

Aqueduct, an artificial channel for conveying water. The term is now generally restricted to large masonry conduits in which the water flows with a free surface. It is not applicable to pipes working under pressure, as the pipe lines through which petroleum is forced, but refers specially to a channel raised above the level of the ground as a bridge to span some hollow. The piers and arches of an aqueduct may be of stone, brick, or concrete. The water channel, if of masonry, must be made watertight. An iron or steel water channel or conduit is often used, and as such pipes are now made of large size and of sufficient strength, they are frequently and preferably employed. In the United States many of the aqueducts carrying irrigation water across valleys are timber structures; trestle bridges are largely used, and the timber channels are called fumes, while wooden pipe of cylindrical section, built up of staves held together by iron bands, is also employed. The Romans made little use of pipes under pressure; they raised the channel on arches to keep it at the proper gradient. Where the height was great, they built two or three tiers of arches one above another; and to make the channel impervious to water, the masonry was coated with stucco. Hewn masonry was generally used, but the Tepula aqueduct at Rome was largely constructed of concrete. Some of these early aqueducts are still in a good state of repair, and continue to carry water; a good example is that at Segovia in Spain, built about 109 A.D.

Before the end of the 1st century A.D. Rome was supplied by nine aqueducts, with a total length of over 270 m., of which about 35 m. was raised above ground on arches. The last of these to be built, the Anio Novus, at one point is 109 ft. above ground-level. It is built above the Aqua Claudia, the two waters flowing in separate conduits on the same arches. The aqueduct Ponte delle Torri, at Spoleto, dates from the 7th or 8th century, and is about 300 ft. high, with two series of pointed arches. In the Roman provinces there were the incomparable aqueducts at Nîmes, at Segovia and Tarragona, at Metz and Mainz, at Antioch, and at Pyrgos, near Constantinople. The ancient Greek world possessed famous aqueducts at Athens (made c. 560 B.C.), at Samos (c. 625), and at Syracuse (still in use). In France, the aqueduct of Maintenon was constructed in Louis XIV.'s time, to bring water to Versailles; it is 4,400 ft. long, over 200 ft. high,

Aqueduct

and has three tiers of arches of about 50 ft. span. The first aqueducts of importance in Great Britain were built towards the end of the 18th century to carry canals. They were of masonry, with the bottom and sides of the canal puddled. In the United States the earliest and most important aqueduct was the Croton aqueduct (completed 1842) to carry water to New York from Croton river, a distance of 38.1 miles. It was constructed of masonry with brick lining, and was 8.64 ft. in height and a cross section 53.34 sq. ft. in area. The Croton aqueduct was followed in 1848 by one for Boston, and this in turn by others for the leading American cities as their systems of water-works developed. In 1890 the new Croton aqueduct was completed, and differed from its predecessor in being nearly all in tunnel. This aqueduct is 30.87 miles in length and is of horseshoe-shaped cross section 13.53 ft. in height and 13.6 ft. in width. Its capacity is 302,500,000 gallons per day, as compared with about 72,000,000 gallons for the old Croton aqueduct. Another recent example of aqueduct construction in the United States is the Wachusett aqueduct, which affords an additional water supply for Boston and vicinity, and whose size and capacity are slightly less than that of the new Croton aqueduct. There were under construction in 1909 an immense new water-supply aqueduct for New York City, to be called the Catskill, and a very long water-supply aqueduct for Los Angeles, Cal.

Few aqueducts (in the sense of bridges) of any length have been made in recent years, as an inverted siphon of pipes serves the purpose, and is much less costly. This feature is a marked point of contrast between the old and new Croton aqueducts in New York. In the first the Harlem River was crossed on the massive granite masonry arched High Bridge, shown in the illustration, while the new aqueduct passes underneath the river, though this section is lined with cast iron. Where the valley crossing is short, however, bridge aqueducts are found. These are generally built of masonry, with a water channel of concrete, iron, or steel, and examples of these are to be seen on all the large water-works of the present day. A notable example of such construction is the Cabin John Bridge of the Washington, D. C., aqueduct, a masonry structure which for many years possessed the distinction of being the largest single stone arch bridge in the world. In the aqueduct supplying the city of Boston there is a granite

Aqueous Humor

bridge structure with seven arches, which crosses the Assabet River. See further under WATER; also Herschel's trans. of Frontinus's books about Water Supply of Rome (1899); Turneaure and Russell's Public Water Supplies (1901).

Aqueous Humor. See EYE.

Aqueous Rocks, the name given to those rocks that have been laid down beneath water, whether in the form of sedimentary deposits, of accumulations of shells and other animal or plant remains, or of chemical precipitates. See SEDIMENTARY ROCKS.

Aquila, an ancient constellation placed s.E. of Lyra, and traversed by the Milky Way. Nova Aquila, photographically discovered by

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Aquila, PONTICUS, a native of Sinope in Pontus, flourished about 130 A.D. He made a translation of the Old Testament into Greek, of which a few fragments survive in Origen's Hexapla. He is said to have been successively a pagan, a Christian, and a circumcised Jew.

Aquila degli Abruzzi. (1.) Province, Italy, in territorial div. Abruzzi and Molise, between the two main chains of the Central Apennines. Cereals, flax, hemp, and fruits are the chief productions. Area, 2,485 sq. m. Pop. (1901) 397,645. (2.) Chief tn. of above; episc. see, and summer resort; stands on a plateau at the foot of the Gran Sasso d'Italia, the culminating knot of the Central Apennines, 55 m. N.E. of Rome

Aquinas

mercial centre, having access to the sea by means of a lagoon now silted up. It was founded in 182 B.C., was strongly fortified by Marcus Aurelius, and in the 4th century A.D. was the fourth city in point of size and population in all Italy; but in 452 it was captured by Attila, who razed it to the ground, the inhabitants escaping to the lagoons in which Venice was afterward built. In the 6th century (the town having been rebuilt by the Ostrogoths) it became the seat of a patriarch of the church, who wielded great political power; but the dignity was suppressed in 1750. Aquileia still possesses an 11th century cathedral, and has a museum full of valuable Roman antiquities. Pop. (1900) 2,319.

Mrs. Fleming in April, 1899, was then of seventh magnitude. Its bright-line stellar spectrum became nebular as it faded. One

of the best known short-period variables is 7 Aquila, which fluctuates from 3.5 to 4.7 magnitude in 7 days 4 hours, and was found by Bélopolsky in 1895 to be a spectroscopic binary.

Aquila, CASPAR (1488-1560), the Latin name of a German theologian, ADLER, who, after suffering imprisonment in 1519-20 for his advocacy of the reformed doctrines, became professor of Hebrew at Wittenberg (1524), and aided Luther in translating the Old Testament. Becoming Protestant pastor of Saalfeld (1527), he was outlawed by Charles V. (1548), but was restored to his pastorate in 1552.

(135 m. by rail viâ Terni). The cathedral, first built in the 13th century, has been more than once injured by earthquakes, and has been recently restored." Saffron is extensively grown in the vicinity. Lace-making gives employment to many of the women. Aquila was founded by the Emperor Frederick II. in 1240, on the ruins of the ancient Amiternum. Pop. (1901) 21,261.

Aquilegia. See COLUMBINE.

Aquileia, or AGLAR, vil., Austria, in Görz and Gradisca, at the head of the Adriatic, 26 m. by rail N.W. of Trieste. It was in ancient times strongly fortified, and, owing to its position at the foot of several Alpine passes, and on the Via Emilia, was the principal bulwark on the N.E. frontier of Italy. It was an important com

Aquinas, THOMAS, 'the angelic doctor,' was the son of the Count of Aquino, near which town, situated between Rome and Naples, he was born about 1226. Having received the elements of his education in the monastery of Monte Cassino, he proceeded to the University of Naples, and in his seventeenth year joined the Dominicans. He afterward studied under the celebrated Albertus Magnus at Cologne; accompanied his master in a three years' sojourn at Paris (where he graduated bachelor of theology); then returned with Albert to the school of Cologne as second teacher and magister studentium. The University of Paris having assumed a bitter hostility to the mendicant orders, Thomas sprang to the defence of the latter with tongue and pen; and having

Aquinas

received the Pope's special commission to act as the champion of the Dominicans, he vindicated their position with such acumen and address that he procured the discomfiture of their chief opponent, William of St. Amour. Although this strife somewhat delayed his academic progress, so that he was over thirty before Paris granted his doctorate, the career of Aquinas was thenceforward a triumphal march. Called to Italy by Pope Urban Iv. in 1261, he lectured with signal success on behalf of the church and his order; in 1272 he was made a professor in Naples; and so great was his devotion to learning, and, be it also said, his modesty, that when the highest ecclesiastical preferments, such as the archbishopric of Naples and the abbacy of Monte Cassino, were offered him, he felt it his duty to decline them one and all. He continued his labors in church statesmanship, public lecturing, and writing till 1274, when he was summoned by Pope Gregory to assist in the settlement of the dispute between the Eastern and Western Churches at a council to be held at Lyons. While on the way his overwrought frame collapsed, and he was carried to the Cistercian monastery of Fossa Nuova, near Terracina, where he died, March 7, 1274. His remains were deposited at Toulouse. He was canonized in 1323, and made a doctor of the church in 1567.

Aquinas's greatest work is the Summa Theologia, which exercised an immense influence in his own and later times, and which even to-day forms the main doctrinal standard of Catholicism. It is designed on a magnificent scale, and its great purpose is to exhibit theology as the synthesis and embodiment of all human knowledge, whether of faith or of reason; in a manner it seeks to realize the famous tenet of Scotus Erigena-namely, the identity of philosophy and theology. The ostensible antagonism between natural and supernatural knowledge formed the problem of Aquinas, as of the scholastics generally; and Aquinas, following in the wake of his master, Albertus Magnus, tasks himself to fuse the two, and to show that they are but supplementary aspects of the one indivisible truth, the natural world and the Christian religion being but the twin channels of the Divine self-manifestation. But it was only after Thomas had, with tireless industry, made himself master of both provinces of learning that he projected their synthesis in his magnum opus, and his other works may be regarded as only marking stages on the two converging lines by which he proceeded to the consummation of his

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labors. Thus, on the one hand, we have his volumes on 'disputed questions,' and his Scripture commentaries (Psalms, Isaiah and Jeremiah, Gospels, Epistles), in which he draws mainly from the fathers; and, on the other, his De Ente et Essentia, his Summa Philosophica contra Gentiles (dealing with natural religion, and of scarcely less importance than the Summa Theologia), and his commentaries on the writings of Aristotle. Thus equipped, he proceeds to his crowning work, the Summa, a complete system of human knowledge, the intellectual antitype of the universal empire and the universal church. The Summa is in three great divisions, treating respectively of God, Man, and the God-Man, the last having been left incomplete at his death.

It should be noted that by revelation Aquinas understands the delivery of a definite body of doctrines, not the actual presence of a divine life in the world; and that with him faith is an intellectual acquiescence in this system of revealed truth, not a personal trust in a divinely-commissioned Saviour. Aquinas marks the zenith of scholasticism. His great opponent was Duns Scotus, the Franciscan doctor, who, taking the will (voluntas) as his principle (as Aquinas had taken intellectus, the understanding), really transferred theology to the sphere of practice, and so, separating again the provinces of reason and faith, inaugurated the decline of scholasticism, and prepared the way for modern philosophy and the reformation. See R. B. Vaughan's Life of St. Thomas of Aquin (1872) and Histories of Philosophy by Erdmann and Ueberweg.

Aquitania, a dist. of Gaul, lying between the Garonne and the Pyrenees. Its inhabitants were one of the three races which originally inhabited Gaul; they were not Celtic, but were more akin to the Iberians in Spain, a preAryan population now represented by the Basques, though the modern inhabitants of Aquitaine are probably to a large extent true descendants of the Aquitani. The district was conquered (57 B.C.) by Cæsar's lieutenants; and again, after a revolt, in the reign of Augustus. The Roman province of the same name was bounded (from 37 B.C.) on the N. by the Loire, on the E. by the Cevennes. on the s. by the Pyrenees, and on the w. by the Atlantic Ocean. The Visigoths, the Merovingians, and the Carlovingians successively possessed the district, and its name in the 10th century became corrupted into Guienne. In 1137, by the marriage of Louis VII. with Eleanor, daughter of William x. of Guienne, it became

Arabi

attached to the French crown. After Eleanor's divorce she married Henry II. of England, and brought him the possession as her dowry. It remained in English hands until the battle of Castillon in 1453, after which it was finally restored to France.

Ara, or ARARA, the great black cockatoo of Northern Australia and the Malayan islands, which is entirely black except the cheeks, which are bare and red. It is the largest known parrot, reaching a length of 30 in., and has a beak so powerful that it cracks such hard nuts as those of the kanari palm, living principally upon them. It is rarely caged.

Ara, an ancient constellation situated to the s. of Scorpio, and possibly embodying a reminiscence of the mound-altar of the Tower of Babel. (R. H. Allen's Star Names and their Meanings, 1899, p. 63.) Among the stars composing it are S Aræ, a short

The Constellation Ara. period variable, and R Aræ, undergoing eclipses once in 4 days 10 hours.

Arabesque, a fantastic scroll and floral decoration employed in the architecture of the Arabs and of the Moors in Spain. The finest examples are to be seen in the palace of the Alhambra, and in the work of Raphael in the Vatican.

Arabi, AHMED, PASHA (1841), leader of the military insurrection in Egypt in 1882. He organized a secret society among the native officers, and headed a revolt. compelling the Khedive, Tewfik Pasha, to dismiss his ministry, and to grant a liberal constitution. Arabi became under-secretary for war, and subsequently minister of war. In this position. being practically dictator, and supported tacitly by the Sultan, he adopted a policy which the British government had to meet by armed force. Alexandria was bombarded by the British fleet. July 11, 1882; and on September 13. Arabi and his army were defeated at Tell-el-Kebir by the British troops under Sir Garnet

Arabia

Wolseley. Arabi fled to Cairo, and, surrendering, was banished to Ceylon (1883). In May, 1901, he was released, and granted a pension of $3,000 a year. See Annual Register for 1882, Long's Three Prophets- Chinese Gordon, Mohammed Ahmed, Arabi Pasha, and article by Wilfrid S. Blunt in Celebrities of the Cen

tury.

Arabia, known to its inhabitants as Jezirat-al-Arab, and to the Turks as Arabistan, is a massive quadrangular peninsula of Asia in the s.w. of the continent, lying between the Persian Gulf and the Gulf of Oman on the E., and the Red Sea on the w., with no natural frontier on the N., the conventional boundary being roughly the parallel of 30° N. Length N. to s., 1,500 m.; average breadth, 800 m.; area, 1,200,000 sq. m., or about one-third of Europe. The Red Sea coast, which is ext remely deficient in harbors, is fringed with shoals and coral reefs; and there are a few small islands as the Strait of Bab-elMandeb is approached, the British island of Perim, at the entrance to the strait, being the most important. The s. coast presents a convex shore to the Indian Ocean, and has a number of good harbors, such as Aden, Dafar, and Keshin. The Oman coast, on the E., has the deep and almost landlocked harbor of Maskat (Muscat); but the sandy shores of the shallow Persian Gulf, to the E. and N. of the Strait of Ormuz, possess no harbor of importance until El Kuweit (Koweit), at its head, is reached. The gulf contains numerous islands, the chief being Bahrein, which is the centre of the gulf pearl fisheries, valued at about $1,500,000 annually. British influence is predominant in the gulf.

Ptolemy's divisions of the country were Arabia Petræa (N.w.and the peninsula of Sinai), Arabia Felix (w. and s. coasts), and Arabia Deserta (all the rest). The modern divisions are the Sinai Peninsula, between the Gulfs of Suez and Akabah; El Hejaz (Hedjaz, the barrier'), fronting the Red Sea, and succeeded by the fertile, well-watered, and well-cultivated country of El Yemen, the littoral from 20° N. to 15° N. being the low-lying sandy strip, covered with coral débris, of Et Tehama; Hadramaut and Mahra, fronting the Gulf of Aden and the Indian Ocean respectively; the mountainous kingdom of Oman, comprising the horn of Arabia: El Hasa, fronting the Persian Gulf; and El Nejd, the oasis-studded middle portion of the interior. In relief Arabia is a table-land (average elevation, 3,500 ft.),

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sloping steeply to the w. and s.w. and gently in other directions, and bordered by highlands which attain their greatest elevation, and are often precipitous and rugged, in Yemen, Hadramaut, and Oman

Arabia

Yemen and elsewhere on the coastal escarpment from 1,200 to 4,000 ft.; also the acacia, which yields gum-arabic; spice and incense trees (Hadramaut), date palms, cotton, maize, and rice,

DOMLYX

Moorish Arabesque Ornament (Hall of Crowns, Alhambra).

(9,900 ft.). The mountain mass of Mount Sinai, on the N.W., is only 365 ft. lower. A low and mainly fertile coast strip lies between the highlands and the sea. The peninsula thus consists of a coastal plain, coast ranges, and a central plateau. El Nejd, the true home of the Arab,' with grassy slopes and narrow productive valleys, is joined to the coast range by the ridge of Jebel Aarud or Imarieh, and is bordered by largely unexplored deserts-the simoom-swept sands of the Nefud and the stony Syrian desert lying to the N., and the arid waste of the Roba'a-el-Khali to the s.

The coasts of Arabia are among the hottest regions of the world. The mean temperature of Aden varies from 75° F. in Jan. to 85° F. in July; but the higher parts of the plateau, which have a great range of temperature and almost no rainfall, experience intense cold on winter nights. Scanty winter rains fall in the N., but in the s. the rains occur in summer or early autumn. some of the mountains of Yemen there are spring rains.

In

The coffee tree flourishes in

are grown elsewhere, especially in Yemen. Senna is cultivated in S. Hejaz and the Tehama, balsam near Mecca, henna on the w. coast, and indigo on the Persian Gulf. Horses and dromedaries are reared in the Nejd, and command high prices; camels, large white donkeys, fat-tailed sheep, goats, and cattle are largely bred. Among wild animals are the ostrich, tiger, panther, lynx, hyæna, and gazelle. Precious stones, silver, lead, and other minerals, are found.

The people (estimated at 3 millions) are mainly Arabs (Bedouins on the borders of the deserts) and followers of Mohammed. The tribes of the Nejd, Hadramaut, Oman, Mahra, and Kara are practically independent. The sultan of Oman, however, is recognized by the British government.

The chief centres of Hejaz (approx. area, 96,500 sq. m.; pop. 300,000), through which pass the pilgrim routes from Syria and Egypt, are Medina, the city of Mohammed's flight and death; Yambo, its port; and Mecca, the prophet's burial place, annually