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ABC, JOAN OF 228 ABCH fixed to the terminals of a battery in such a position that their extremities are one-tenth of an inch apart. ARC, JOAN OF. See Joan of Arc. ABCA, a genus of conchiferous mol- lusks, the typical one of the family arcadse. The shell is strongly ribbed, or cancellated, hinge straight, with very numerous transverse teeth. They are uni- versally distributed, but are commonest in warm seas. They inhabit the zone from low water to 230 fathoms. Of the recent species. A. noas, A. tetragona, A. lactea, A. raridentata, and A. barbata occur in England. The fossil species are found in the United States, Europe, and southern India. ARCACHON (ar-ka-shoh'), a bathing place which has grown up since 1854, on the S. side of the Bassin d'Arcachon, 34 miles S. W. of Bordeaux, France. Its main street stretches 2^ miles along the shore, with the pine forest immediately behind. Its numerous villas among the first are much frequented in winter by invalids afflicted with lung disease. Scien- tific oyster culture is practiced here on a large scale. Pop. about 12,000. ABCADE, a series of arches of any form, supported on pillars, either inclos- ing a space before a wall, or any building which is covered in and paved; or, when used as an architectural feature for orna- menting the towers and walls of churches entirely closed up with masonry. The term is also applied to a covered pas- sage having shops on either side of it. Two arcades inscribed in a greater arcade are called geminous arcades. ABCADIA, the classical name of middle Peloponnesus, now forming the modern province of Arkadia, in the Morea, Greece. It occupies a high table- land having on the N., Achaia,E., Argolis, W., Elis, and, on the S., Laconia and Messenia. Area 1,600 square miles. It is intersected by mountain ranges, some of which are very lofty, and contains plains of some extent. Its principal river is the Roufia (Alpheus) , the largest in the Morea. Lake Stymphalus, of clas- sic mention, is found here. The inhab- itants still retain their primitive mode of life as shepherds, pursuing a migratory existence. Chief towns, Tripolitza, Lon- dari, Karitena, etc. Many interesting ruins are seen here, among them the re- mains of the cities of Phigaleia, Megalop- olis, and Pallantium. Pop. about 175,000. From its first inhabitants, the Pelasgi, the land derived the name Pelasgia. In later times it was divided among the 50 sons of Lycaon into kingdoms, and re- ceived from Areas the name Arcadia. In the course of time the small kingdoms made themselves free, and formed s con- federacy. The principal were Mantirvea, where Epaminondas obtained a victory and a tomb (now the village of Mondi), Tega (now Tripolitza), Orchomenus, Phenus, Psophis, and Megalopolis. Their chief deity was Pan; their chief business, the breeding of cattle and agriculture. This occasioned the pastoral poets to select Arcadia for the theater of their fables. ABCESILAUS (ar-ses-e-la'us), a Greek philosopher, founder of the New Academy, was born at Pitane in JEoUa, Asia Minor, 316 b. c. He ultimately be- came the head of the academic school or those who held the doctrines of Plato ; but he introduced so many innovations that its philosophic character was com- pletely changed in the direction of scep- ticism. His great rivals were the Stoics. He denied the Stoical doctrine of knowl- edge, which he affirmed to be, from its very nature, unintelligible and contradic- tory. He also denied the existence of any sufficient criterion of truth, such as the "irresistible conviction" of the Stoics, and recommended abstinence from all dogmatic judgments. He died in 241 B. C. ABCH, in architecture, a series of wedge-shaped stones or bricks, so ar- ranged over a door or window in an edi- fice for habitation, or between the piers of a bridge, as to support each other, and even bear a great superincumbent weight. The stones and bricks of a truncated wedge shape used in building arches are called voussoirs. The sides of an arch are called its haunches or flanks. The highest part of the arch is called its crown, or by the old English authors the scheme or skeen, from the Italian schiena. The lowest voussoirs of an arch are called springers, and the central one which holds the rest together the key- stone. The under or concave side of the voussoirs is called the intrados, and the outer or convex one the extrados of the arch. A chord to the arch at its lower part is called its span, and a line drawn at right angles to this chord, and extend- ing upward to its summit, is called its height. The impost of an arch is the portion of the pier or abutment from which the arch springs. If the height of the crown of an arch above the level of its impost is greater than half the span of the arch, the arch is said to be surmounted. If, on the contrary, it is less, then the arch is said to be surbased. The curved arch was known to the As- syrians and the Old Egyptians.