similar arcs. Circular arcs have the same numerical measure as the central angles which they subtend, and hence are commonly said to measure and to be measured by those angles. Like their subtended central angles, arcs may be considered as positive or negative and as exceeding 360° (see Angle). An arc is dis- tinguished as major or minor, according as it 13 greater or less than a semi-circumference. The arc equaling in length the radius of a circle is called a radian; it is nearly 57° 17' 44. S". There are, therefore. 2 v radians in a circumference.
ARC, Electric. See Electric Arc and Electric Lighting.
ARC, Joan of. See Joan of Arc.
ARCACHON, iir'ka'shoN'. A French town and favorite watering-place on the Bay of Biscay, in the Department of Gironde, which has grown up since 18.54, on the south side of the Bassin d'Arcachon, thirty-four miles southwest of Bordeaux by rail. The fine broad sands are admirably adapted for bathing, and the place is sheltered by sandhills covered with extensive pine woods of the Landes. Its main street stretches two and one-half miles along the shore, with the pine forests immediately be- hind. The climate is always temperate, averaging in summer 47° F. and in winter 41°. Its numerous villas among the firs are much frequented in the winter by invalids afflicted with lung disease. Scientific oyster culture is practiced here on a large scale. Pop., 1901, 82.59.
Consult Airachon (Paris, 1899).
ARCADE' (Fr., from Lat. amis, bow, arch, vault). A row of arches supported by columns or piers, either having an open space of greater or less width behind them, or in contact with masonry. The arcade in Christian architecture corresponds to the colonnade in classical archi- tecture ; the difference between them is mainly in the substitution of arches for the straight architrave. The term 'arcade' is sometimes ap- plied to the row of piers, or columns and arches, by which the aisles are divided from the nave of a church, or by which cloisters are inclosed; but it is more generally confined to those series of smaller arches which are employed simply for purposes of ornamentation. They form the main decorative feature of both outside and inside meditEval architecture, especially in the form of real or blind galleries, adding a play of light and shade, a richness of detail, and a variety of form that contrast with the early Christian simplicity and the exclusive use of color by the Byzantines. The term is also applied, im- properly, to a glass-covered street or lane with a row of shops or stalls on each side.
AR'CADELT, Jacob. A Flemish composer who assisted in founding the classical Italian school of music. The date of his birth is un- certain, but is believed to have been during the first quarter of the Sixteenth Century. His works are among the masterpieces of contra- puntal music of the Middle Ages. He was the most popular composer of his day, and his popu- larity induced many persons, for business rea- sons, to add his name to works written by others. During a residence in Rome (1539-55), as teacher and as singer in the Papal Chapel, he composed many madrigals. His works also in- clude motets and masses. Arcadelt probably died about 1570-75, while in Paris with Cardinal Charles, Duke of Guise, whose service he entered in 1557. Consult: Burney, General History of Music, Vol. III. ( London] 1789) ; Ambros. Ge- schichte dcr Musik, Vol. II. (Breslau, 1862-82).
ARCADES, ar'ka-dez. A masque written by John IMilton in 1634 and published in 1645. It was acted shortly after Comus, before the Countess-Dowager of Derby, wife, first of Fer- nando, Earl of Derby, and afterwards of Thomas Egerton, liord Ellesmere, when she was living at Harefield, near Uxbridge. It was set to music by Mr. Lawes at the same time. In it the Countess's guests appear on the scene in pastoral habit and move toward the seat of state with a prefatory song of compliment. A "genius of the wood" then comes forward and describes the significance of the occasion, after which the piece closes with two more songs of flattery.
ARCA'DIA (Gk. 'ApKaSla, Arkadia). The middle and highest part of the Peloponnesus, bounded on the north by Achaia, on the east by Argolis, on the south by Messenia and Laconia, and on the west by Elis. According to Pausanias, it derived its name from Areas, the son of Callisto. Next to Laconia, Arcadia was the largest country in the Peloponnesus. It had an area of 1800 square miles, and was girt round by a circle of mountains, which cut olT to a large extent its conununication with the rest of the peninsula. Mountains also intersected it in different directions, forming a number of small cantons. The western part of what was anciently Arcadia is wild, bleak, and rugged, and covered with forests : the eastern is more fertile; and in the southeast are two plateaus, in which lay the chief ancient cities. The loftiest peak in Arcadia is Mount Cyllene, in the northeast, 7790 feet. Tlie small rivers are either tributaries of the Alpheus (q.v.), or empty into inland lakes drained by underground channels ikatavothra) . The chief cities were Tegea (q.v.) and Mantinea (q.v.) in the southeast, and the great city. Megalopolis (q.v.), founded in B.C. 370 by Epaminondas as the capital of the Arcadian Confederacy. Further north were Orchomenus. Pheneus, Clitor, and Psophis. Owing to its isolation, Arcadia remained little affected by the Dorian conquest of the Peloponnesus, and its inhabitants were regarded as belonging to the original population of the peninsula; a belief confirmed by their dialect, which preserves some early forms and shows strong resemblances to the Cyprian. The nature of the country also prevented any lasting union among the inhabitants, and enabled the Spartans
