Examples of arches are the Cloaca Maxima, built about 641 s.c., with three concentric rings of voussoirs, inside diameter, 14 feet; the Pont du Gard, built by Agrippa, 19 }Lc., which has semi-circular arches, built of Pozzuolani concrete with stone or brick facing. The long est masonry span in Europe is the railway bridge over the Pruth, Jaremcze, Austria, 213 feet wide with a rise of 59 feet, and built in 1892. This shows hollow spandrels, which are constructionally and artistically correct. The Cabin John Bridge, near Washington, D. C., which carries an aqueduct and highway, 220 feet. The Wheeling, W. Va., Main St. Bridge, built in 1892, 159 feet long, 28 feet rise, is de ceptive, as spandrels are hollow, but appear to be solid. The great arch now built for the cathedral of Saint John the Divine, New York, is of masonry resting on the top of piers 86 feet high. The span is 114 feet from outside to outside of voussoirs. In 1896 was built the first large concrete arch in the United States, 40 feet span, seven feet rise, all of con crete. This was for a highway bridge. There is also a 60-foot arch of steel-concrete in Franklin Bridge, Forest Park, Saint Louis, Mo. "Concrete reinforce& is the name given to the combination of concrete with steel or iron in building. Steel-concrete, armored concrete,
beton ormi, tiniest artn4, are various terms for such construction, now coming into frequent use.
The Melan arch system was developed by Prof. Joseph Melan, using stiff steel ribs or beams embedded in concrete to form the arch ring, following Austrian experiments. Exam ples of Melan arch are found in Eden Park, Cincinnati, Ohio, 70 feet span; railway bridge over Southern Boulevard,• Detroit, Mich.; road bridges over the Passaic, Paterson, N. J.• Kan sas Avenue, Topeka, Kan., this being the longest, having five arches, one of 125 feet, two of 110 feet each, two of 97 feet each; Hyde Park-on-Hudson for F. W.-Vanderbilt, 75 feet span; a foot bridge in park, Stockbridge, Mass., 100 feet span, rise 10 feet, only nine inches thick at crown; three-hinged arch, Steyr, Hun gary, span 137 feet, rise only nine feet, or one fifteenth of span. The Mother method is concrete with wire netting embedded near the soffit. Arches of long span and slight rise in construction are being made with the Guastavino system of cohesive construction, which is practically a revival of ancient and mediaeval building methods. See ARCH, MEMO RIAL AND TRIUMPHAL; BRIDGE; BUTTRESS; VAULT.