BRIDGE BUILT WITH ARCHES, its anatomy. Professor Fleeming Jenkin says: “An arch may be of stone, brick, wood, or metal. The oldest arches are of stone or brick. They differ from metal and from wooden arches, inasmuch as the compressed arc of materials called the _ring_ is built of a number of separate pieces having little or no cohesion. Each separate stone used in building the _ring_ has received the name of _voussoir_, or archstone. The lower surface of the ring is called the _soffit_ of the arch. The _joints_, or bed-joints, are the surfaces separating the voussoirs, and are normal to the soffit. A brick arch is usually built in numerous rings, so that it cannot be conceived as built of voussoirs with plane joints passing straight through the ring. The bed-joints of a brick arch may be considered as stepped and interlocked. This interlocking will affect the stability of the arch only in those cases where one voussoir tends to slip along its neighbour. The _ring_ springs from a course of stones in the abutments, called _quoins_. The plane of demarcation between the ring and the abutment is called the _springing_ of the arch. The _crown_ of an arch is the summit of the ring. The voussoirs at the crown are called _keystones_. The _haunches_ of an arch are the parts midway between the springing and the crown. The upper surface of the ring is sometimes improperly called the extrados, and the lower surface is more properly called the intrados. These terms, when properly employed, have reference to a mathematical theory of the arch little used by engineers. The walls which rest upon the ring along the arch, and rise either to the parapet or to the roadway, are called _spandrils_. There are necessarily two outer spandrils forming the faces of a bridge; there may be one or more inner spandrils. The _backing_ of an arch is the masonry above the haunches of the ring; it is carried back between the spandrils to the pier or to the abutment. If the backing is not carried up to the roadway, as is seldom the case, the rough material employed between the backing and the roadway is called the _filling_. The _parapet_ rests on the outer _spandrils_.” BRIDGE CHAPELS AND ORATORIES, 82, 208, 209, 216-17, 218-19, 225-39, 241-6, 256. BRIDGE CROSSES AND CRUCIFIXES, 96, 230, 246-7. BRIDGE DECORATION, 193-4, 195-6, 201, 215, 227, 286, 304, 305, 311, 312, 316, 318-28. BRIDGE FRIARS, or Pontist Brothers, the _Frères Pontifes_, 93, 236, 296, and _footnote_. BRIDGENORTH, formerly the bridge there had a chapel, 231; it has shelter-places for foot-passengers, 258 _footnote_. BRIDGES WITH WIDE ARCHED SPANS, 309-10.