ARC ! 



instead of a piazza or ambulatory. 

 bsuart. 



AR'CAD.E, a family of marine bivalve 

 shells, of which the genus area if the type. 

 ARCA'DI.VNS, a society of Italian poets 

 in Rome, established in the latter half of 

 the 17th century, for the improvement of 

 taste, and the cultivation of Italian poetry. 

 It took the title of The Academy o/^rca- 

 dians; in conformity with which they 

 pretend to imitate the pastoral life of 

 the Arcadians (inhabitants of Arcadia, 

 the Greek Switzerland). 



ARC-BOCTA.:<T, Fr, from arc and botiter, 

 to abut. An arched buttress formed of a 

 Hat arch, abutting against the feet or 

 sides of another arch or vault to support 

 them and prevent their giving way in 

 that direction : called also a flying bjittress. 

 ARCH, probably from of%;> beginning, 

 origin; Fr. arc, arch. 1. In geometry, 

 part of a circle, not more than a half. 



Among modern mathematical writers 

 this form of the word is disused, being 

 replaced by arc (q. v.), except as re- 

 stricted to its signification among ar- 

 chitects and mechanics. 

 2. In architecture, a mechanical ar- 

 rangement of separate inelastic bodies in 

 the~line of a curve, which preserve a 

 given form when resisting pressure. A 

 concave structure of stone or brick raised 

 upon a mould in the form of an arc of a 

 curve, and serving as the inward support 

 of some superstructure. The arch may 

 be supported by the form of its own curve, 

 the stones acting against each other, and 

 resisting with the force by which they 

 would otherwise fall ; or it may be con- 

 structed of wood or iron, and supported 

 by the mechanism of the work. 



The lateral supports of an arch are 

 abutments or Hutments, and the internal 

 supports are piers. The first or under- 

 most stones at A and B of the arch are 

 D' 



termed springers, and the line A B on 

 which they are placed is called the 

 springing line or reins of the arch. The 

 upper end of the pier on which the 

 arch rests is the impost or platband. 

 The stones ranged in the curvature of 

 the arch are archstonesor voussoirs. The 

 whole interior curved surface of the 

 arch A Ii C, is called the intrados by 



i ARC 



geometers, and toffet by architects, or 

 popularly the arch. The extrados is 

 the convex surface A'D' B'. The span, 

 called by geometers the chord o} the arch, 

 is measured from the lines where the 

 intrados rises from the impost. The 

 rise o/ the arch, or, geometrically, the 

 versed sine, is the distance CD of th 

 highest point of the intrados above the 

 chord line A B C. The highest point 

 D of the intrados, is by geometers called 

 the crown or vertex, but by the work- 

 men the underside o/ the crown , the crown 

 with them being the upper end of the 

 key-stone, or stone which connects the 

 two semi-arches A D and C D at D. 

 These semi-arches are called haunchei. 

 or hances, or flanks, and the spaces 

 above these, being the outer walla, 

 forming the elevation of the arch, is 

 the spandrels, or, collectively, the span- 

 drel-wall. Sometimes small circular 

 arches are constructed through the 

 spandrel and haunch walls, mostiy 

 over piers in stone bridges : these are 

 called ox-eyes by the workmen. 

 ARCH, chief, from aqyi : used as a sylla- 

 bic prefix to words, to denote the highest 

 degree of their kind, whether good or 

 bad. 



ARCHXOL'OGY, from a.gra,t6;, ancient, 

 and Xej'e?, a discourse. The science or 

 subject of antiquities, especially of Greece 

 and Home. 



Aa'cHAisx, Gr. from %cws?, ancient. 

 A term used by ancient chemists and 

 physicians, to imply the occult cause of 

 certain phenomena. 



ARCHBISH'OP, from arch and bishop. The 

 name of a church dignitary of the first 

 class. 



The title was introduced about A.D. 

 340. England has two archbishops, 

 that of Canterbury and that of York, 

 who are called primates and metropoli- 

 tans. The archbishop of Canterbury 

 had anciently jurisdiction over Ireland", 

 and was styled a. patriarch, and is still 

 accounted the first peer of England, 

 and next to the royal family. He has 

 the precedence of the dukes and all the 

 officers of the crown. 

 AHCHBC'TLER, one of the great officers 

 of the German empire, who presents the 

 cup to the king on solemn occasions. The 

 office belongs to the king of Bohemia. 



ARCHCHAM'BERLAIN, an officer of the 

 German empire, much the same as the 

 great chamberlain in England. 



ARCfcCHAN'cELLoa, a high officer who 

 in ancient times presided over the secre- 

 taries of the court. 



ASCH'COUNT, a title formerly given to 

 the earl of Flanders, on account of his 

 great power and riches. 

 ARCH'UEACOX-, from arch and cfeaoou. An 



