portion and form of the column, its capital and its base, but also the composition and proportion of the entablature supported by the column and the distance of the columns from each other. These details differed in the different orders, and also, within well-defined limits, in the same order. The classification of the orders was made after Grecian architecture had ceased to be practiced, and is that of Vitruvius, ab. 14 B.C. The Grecian orders were the Doric, Ionic, and Corinthian. The occasional employment, notably in the Erechtheum at Athens, of representations of human figures, instead of columns, to support an entablature, has led some writers to add a

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monly a height of 14 diameters, and decorated with the leaves of the acanthus conventionally designed and arranged. The column itself is ten diameters in height. The only complete example of the order in Greece is the choragic monument of Lysicrates at Athens.

The Roman temples were imitated from those of the Greeks, and the imitation was in the main a debasement, tending to substitute an expression of luxury and magnificence for the more intellectual qualities of simplicity, purity and harmony of the originals. There is no completely developed Roman example of a Doric temple, and none of an Ionic temple that does not lose by comparison with the Greek. With the Corinthian order the case was somewhat different. As used in Greece, the elegance aimed at in this order degenerated into feebleness,

Parthenon, Athens, Restored (Greek Doric).

Caryatic order. The Parthenon at Athens, the most famous of Grecian buildings, is an octastyle (having eight columns in front), peripteral (entirely surrounded by columns) Doric temple. In the Doric order the stylobate (base) is continuous. each shaft resting directly upon it, without the intervention of a separate base; the columns are fluted, tapering slightly from the base, not regularly but with a slight outward curve (entasis), and four to six diameters in height. The capital consists of a necking (echinus), a convex curve (ovolo), and a straight-sided abacus. The entablature is subdivided into architrave, frieze and cornice, each of these members being subdivided. The frieze is a succession of triglyphs (upright members, each bearing two grooves), and metopes (square panels), the latter occupied by the sculptured and tinted reliefs that constitute the chief decoration of a Doric temple. Above the entablature at each end is the pediment, also occupied by a group of statuary. The Ionic order is supposed to have been derived from Asia, and Assyrian and Persian examples support this supposition, as respects its most distinguishing feature, the voluted capital. The Ionic order is more slenderly proportioned than the Doric, the column being, in the best examples, more than nine diameters in height, of which the molded base occupies of a diameter, and the capital, including the necking, to . The entablature is subdivided as in the Doric order, but the frieze is continuous, the decoration being the richly carved moldings of the capital, architrave, and upper member of the cornice. Grecian Ionic

Erechtheum, Athens (Greek Ionic).

temples were seldom or never peripteral, being restricted to a portico at each end. The Corinthian order is doubtless of Grecian origin, its distinguishing mark being a capital much taller than that of either of the other orders, attaining com

especially in the design of the capital. The Roman architects perceived this weakness and undertook to remedy it by developing the volutes at the angles, and confining the foliage more closely to the bell of the capital. These changes improved the capital as a structural member. The temple of Jupiter Stator in Rome is the best example. The volutes were finally developed into the proportions of an Ionic capital, being still set diagonally, and the foliage beneath retained. This modification is the distinguishing feature of the Composite, the fourth of the five orders recognized by Vitruvius, the fifth being the so-called Tuscan, a Roman modification of the Doric, commonly used on a much smaller scale, in which the column is not fluted, is provided with a separate base, and is crowned with a capital materially modified from the Greek Doric, though retaining its several members. The arch was first extensively employed by the Romans as a constructive expedient, together with its derivatives, the dome, the half-dome, the wagon, or continuous vault, and the cross vault; but none of these structural features was developed, or made the basis of the design. Columns were employed, except in the temples, as decorative features, and applied to the faces of the piers, which were the real supports, the column never appearing in classical Roman architecture, except in part of the order, and in connection with an entablature, which, when used in connection with an arched construction, was not a continuous, horizontal member, but a fragment of a lintel, obviously performing no economical function. For this reason Roman architecture has been said to be transitional between the Grecian, in which the construction of post and lintel was the basis of the architecture, and the Romanesque, in which the arched construction served the same purpose. The epithet Classic is restricted to the works of the Greek and Roman builders, in which the Grecian orders were employed, and to modern works in imitation of these.

Roman Doric Order.

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During the decline of the Empire and after its fall, the Roman methods of construction were adopted in all the countries in which the Romans had left monuments, and in these the influence of Roman building continued to be traceable throughout the whole of the Romanesque and Gothic periods, till 1400. The Basilica, a building of purely Roman type, is memorable as having furnished the type of the Christian church. It was a combined market-place, or merchants' exchange, and tribunal. It was a hall, its length twice to thrice its width. with a roof supported by columns; on each side of the colonnade was a lower building. The tribunal or court-room had a recess, often apsidal in plan, at one end, sometimes at each end, as in Trajan's at Rome, sometimes at one side, as in that of Fano, designed and described by Vitruvius. The basilicas were commonly of wood; our knowledge of them is derived from descrip; tions, from fragments of ground-plans preserved in tabletsand from examinations, as that of Trajan and of Pompeii,

Pantheon, the same rationalizing process which the early Romanesque builders applied to the wall-arch. The St. Sophia, in Constantinople, 532-537, is as clearly the earliest example of Byzantine building as the palace of Diocletian of w. Romanesque. In this is found the origin of the domed architecture of Mahometan countries, of the mosques of Spain, Egypt, Persia and India, as well as of the Greek Church architecture, including that of Russia. On the Italian shore of the Adriatic the style derived from Rome through Constantinople was practiced together with that derived directly from Rome. St. Mark's at Venice, consecrated 1085, and San Vitale at Ravenna, 530, are distinctly Byzantine buildings, and the style penetrated as far as Perigneux (St. Front, 1047) and even to Aix-la-Chapelle (Charlemagne's chapel, 796-804). These domed churches are exceptional; the Roman basilica remained the church type throughout western Europe. The desire for a durable roof of masonry was the motive of the development of Romanesque architecture. The mechanical difficulty of bridging wide spaces with masonry is illustrated in some Romanesque churches by the fact that while the aisles were roofed with groined vaulting, the wider naves were covered with continuous wagonvaults, as with roofs and ceilings of timber. The difficulty and awkwardness of uniting semi-circular arches of different spans and heights led to the introduction. in France, ab. 1150, of the pointed arch, which had been employed by the Arabian builders in Egypt, three centuries earlier. The application of this device made comparatively easy a more complicated system of vaulting than had before been possible. Within less than a century after its first appearance the vault-and-buttress system of the cathedrals was fully developed, while a system of modeling, with reference to the expression of function, had been extended to all the details of buildings. Gothic architecture prevailed throughout Europe during the 13th and 14th centuries. During the 15th the revival of letters in Italy led to a diligent study of the forms of classical architecture, and the result was the so-called Renaissance, in which these forms were again introduced. The only new structural form then introduced was a cupola, much taller in proportion to its diameter than that employed by the Roman or Byzantine builders. The first example of this was furnished by Brunelleschi in the dome of the cathedral of Florence, 1420-44; it was followed by Alberti, Bramante, and Michelangelo (in St. Peter's at Rome), in which the dome was the dominating feature of the building, both within and without. Architectural details were borrowed or compiled from classical Roman architecture. The style thus formed has continued to prevail throughout Europe. In France, some parts of Germany. Great Britain, and America, churches are often designed in Romanesque or Gothic forms; and in these countries, especially in England, Germany, and the U. S., systematic efforts have been made, within the past half century, to revive medieval architecture, and to apply its principles to secular as well as to ecclesiastical structures. In spite of these efforts, the Renaissance continues to be the architectural style most in vogue with all civilized nations.

Architrave. In classic architecture, the lowest member of the entablature, a beam resting directly upon the abaci of the capitals. In Grecian Doric it is quite plain and composed of a single course of stone. In Ionic and Corinthian it is composed of three courses, with well-defined joints, but otherwise without ornament. In Roman the joints are often enriched with decorated moldings.

Archivolt. Molding on the face of an arch and following its curve.

Archons. Highest magistrates at Athens. After the abolition of the regal office an archon for life was elected; in time the term was made ten years; in 684 B.C. it became annual, and the office was shared by nine colleagues, who divided the several functions. One presided, after whom the year was named, another directed religious rites, and yet another commanded the army. During a long period they were selected by lot from among the wealthier citizens.

Archosauria. Division of Reptilia including the orders: Anomodontia, Crocodilia, Ornithoscelida, and Ornithosauria. In these forms two post-orbital bars are present, united to quadrate bone by suture. Also, a group of fossil Reptiles, including the Theriomorpha, Dinosauria, and Ornithosauria.

Archpresbyter, or ARCHPRIEST. Order once next to bishop, powerful till 12th century: now resembling, in Greek Ch., Anglican deans, and in R. C., rural deans.

ery hall of the Paris Exposition of 1889 had a central arch of

364 ft. span, and that of the Liberal Arts building of the Chicago Exposition of 1893 a central span of 368 ft., the largest arch roof ever built.

Arch, TRIUMPHAL. Originating with the Romans; built across roads, or at the entrance to cities, in honor of successful generals and foreign conquests. In Rome, those of Drusus, Titus, Septimus Severus and Constantine are notable; the latter built of materials from an arch of Trajan, destroyed for

Triumphal Arch of Constantine.

the purpose. There are fine specimens at Beneventum and Aosta, and several in France.

Archytas, d. ab. 350 B.C. General of Tarentum, Pythagorean philosopher, supposed friend of Plato and Aristotle, eminent mechanician. Fragments of his writings remain.

Arcifera. Order of Anura, forms having the breastbone soft and cartilaginous; including the Bufonida (Toads); the Discoglossidae, e. g., Alytes; Cystignathidae, e. g., Hylodes; Pelobatida, represented by Scaphiopus; and the Hylide or Tree Frogs.

Arc Lamp. The method first devised for producing the electric light consisted in bringing the carbon terminals of a sufficiently powerful generator into contact and then separating

Brush Arc Lamp.

them. The current continues to flow across the gap, developing, in consequence of the great resistance there, a most intense

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heat, which raises the terminals to vivid incandescence. If the carbons be horizontal, the upward current of air causes the luminous stream to assume an arched form; whence the name electric arc." The electric arc lamp is a device for holding the carbons of an are light and for maintaining the light conis which has given the name "regulator" to such lamps. Two stant by means of suitable mechanism. The latter function it distinct operations must be performed by the regulator; first, it must separate the carbons to produce the light; and second, it must feed these carbons forward as fast as they are consumed, so as to preserve the light from extinction and to keep the length of the arc constant. It may be also necessary, as in the case of focusing lamps, for the regulator to perform a third function; viz., that of keeping the are constant in position. Moreover, lamps must be capable of operating independently, so as to be used in a circuit with others without being effected by their variations.

In commercial lighting, lamps are usually arranged in series, and the Brush lamp may well serve as a type of this class. In this a ring clutch, surrounding the upper carbon holder, and controlled by an electro-magnet in series with the carbons, lifts this holder as soon as the current passes, and thus separates the carbons and produces the light. Moreover, this magnet is antagonized by a second one in shunt circuit with it, for the purposes of regulation; since, whenever the arc becomes too long and is in danger of extinction, the increased resistance thus developed throws more current into the antagonizing shunt magnet, enabling it to overcome the main magnet and so to allow the carbons to feed together. Since the result is due to the differential action of two magnets, one situated in the main and the other in the shunt circuit, such lamps are generally known as shunt differential lamps.

As the positive carbon burns away about twice as rapidly as the negative one, an additional device must be applied in focusing lamps to feed the former twice as fast as the latter. Of arc lamps those used for search-lights are the most powerful. For this purpose the arc is placed in the focus of a parabolic

mirror.

circle which passes any fixed point during the driving contact Arc of Contact. In toothed gearing, the arc of the pitch of two teeth. It should never be less than the distance between the centers of two teeth (the circular pitch of the wheel), or else the driver would cease acting on one tooth before the next tooth was engaged; hence a jump and shock would occur over the space where the driver met no resistance. The arc of contact is usually or twice the circular pitch, and is limited by the condition of not having excessive length to the teeth outside the pitch circle, which would cause unusual obliquity of action of the teeth, and produce greater friction.

Arcola. Town of Lombardy, site of three battles, Nov. 1417, 1796, between Bonaparte and the Austrians under Alvinzy, who lost 18,000 men. The French lost 15,000 and became masters of Italy.

ras.

Arcot, or ARKAT. City of s. Hindustan, 65 m. s. w. of MadIts capture by Clive, Aug. 1751, was the beginning of British power in India. It is the chief town of two districts of the Madras presidency, n. and s. Arcot, which have an area of ab. 12,100 sq. m., and a pop. of ab. 3,700,000.

Arctic Ocean. That part of the sea lying n. of Asia and N. America, and surrounding the N. Pole. It communicates with the Pacific through Behring Strait, with the Atlantic through Smith Sound and the broad passage between Greenland and the Scandinavian peninsula. It contains numerous islands, many of them very large, as Nova Zembla, Spitzbergen, New Siberia, and Wrangle Land, besides the great archipelago n. of N. America. Its shores are icebound. Many navigators have explored it to find the N. W. Passage. Parry reached lat. 82° 45' N. in 1827; Kane attained lat.81° 22' in 1854, and found reason to infer an open sea around the pole; Lockwood of Greeley's expedition, 1882. reached 83° 24', which is the highest point thus far attained. There are floating masses of ice 200 ft. in height, and ice-fields 100 m. in length. Capt. Ross measured a berg which rose 325 ft. above the water. (See Map, page 88.)

Arctinus. Probably 7th cent. B.C. Greatest of the Cyclic Greek poets. The epics Ethiopis and Destruction of Troy were attributed to him; another is also ascribed to him by some. We have a synopsis of these, and fragments.

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Panda (Elurus fulgens).

Arditi, LUIGI, b. 1822. Italian composer and opera conductor in London and America; author of a waltz Il Bacio, and the operas I Briganti, 1841; Il Corsaro, 1846; La Spia, 1856.

Are. Metric unit of Surface; a square whose side is ten

meters.

Area. Limited surface considered as subject to measurement. Algebraic expressions for area contain two linear factors. Similar areas are to each other as the squares of homologous elements.

Area Germinativa, or EMBRYONIC AREA. Part of the surface of large eggs, upon which the embryo lies. Small eggs are practically the whole embryo.

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Area of High Pressure. Region over which barometric pressure is higher than in the neighboring regions. On meteorological charts and reports these areas are for brevity frequently designated as High." Special local high areas ocridges produce a belt of average high pressure around the globe.

Arctomyinæ (GROUND SQUIRRELS). Sub-family of Sciuridæ, including the Arctomys (Marmots), Cynomys (Prairie-dog), Spermophilus (Ground Squirrels), and Tamias (Chipmunk). Arctomys. The Marmot, Woodchuck, or Ground-hog is the largest member of the Squirrel Family (Sciuridae). See ARCTOMYINÆ. They measure up to two feet in length, are plump, have a short bushy tail, low ears, and coarse hair. Cheek pouches are rudimentary, and the pollex bears a flat nail. A. monax is the woodchuck proper, which lives solitarily, hibernates in winter, and comes out in spring, whence its use as a weather prophet. Marmots like prairie-dogs generally live in colonies.

Arctopithecini, or HAPALIDE. Group of Simiada, including the Marmosets. The nose is of the platyrhine type; the pelage soft and abundant; the tail is long, bushy, and nonprehensile. There are no cheek pouches or natal callosities; the fore-limbs are shorter than the hind. There is no opposable thumb, and the digits are all clawed except the opposable hallux, which has a flat nail. The number of teeth is the same as in man, but there is a præmolar more and a molar less in each series. The molar teeth have pointed cusps. They are S. American monkeys, about as large as squirrels; several species are domesticated and kept as pets. The coloration is variable; many have bands on the tails, and some (Midas) have peculiar crests of hair and whiskers. They are not hardy. The female usually bears twins or triplets after but three months' gestation. The cerebral hemispheres cover the cerebellum. They require insects as food.

Arcturus =a BOOTES. Star of first magnitude. Right ascension 14h. 10m. 36s. Declination 19° 45′ 38′′ N.

Arcuata. See CRABS.

Arcus Senilis. White ring which forms around the margin of the cornea after middle life; occasionally seen in those much younger. It is of little importance except when it extends sufficiently to obscure the central portion of the cornea. Ardeida. Herodii, especially Ardea (Herons), Botaurus

π

π

Arenal Measure of an Angle. Sometimes called " measure. An angle may be measured by the ratio of the intercepted arc (having center at the angular vertex) to its radius. The unit, called Radian, is the arc equal in length to the radius, and equals in degree measure 57° 17' 44.80"+. In this measure 180° =#: 90° 0.01745+. Arenicola. A tubicolous Annelid, with small præstomium, without tentacles. The proboscis is beset with papillæ, or branched gills on the posterior segments. They burrow in the sand.

ᅲ

60° 2

3

10

work of fine fibers which cements together the elements of the Areolar Tissue. Connective tissue or interlacing netorgans and tissues, and loosely joins structures which adjoin each other; e.g., the skin and the muscles beneath it.

Areolation. Reticulated areas of leaves; especially in ferns and mosses, and the markings on diatoms. Areometer. Instrument for measuring the rarity or density of a liquid. See HYDROMETER.

Areopagus. Hill of Ares or Mars, w. of the Acropolis in Athens; hence the most ancient court of Athens, which met

Areopagus.

there. Solon changed its constitution; it became less aristo