A treatise on architecture and building construction . Fig. 60. rests on such a small footing, it is liable to separate fromthe arch, thrusting out of place some of the lower such a case, the lower voussoir a should be cut so as toextend to the corner of the wall, until the distance ^ (^ is atleast 8 inches; more than this should be allowed if the wallis very heavy. 109. Moltling;.—Arches are often decorated with moreor less elaborately dressed stone, known as label and soffitmoldings. The former is sometimes cut in the ring stones,but oftener forms a separate course of thin stone. I
A treatise on architecture and building construction . Fig. 60. rests on such a small footing, it is liable to separate fromthe arch, thrusting out of place some of the lower such a case, the lower voussoir a should be cut so as toextend to the corner of the wall, until the distance ^ (^ is atleast 8 inches; more than this should be allowed if the wallis very heavy. 109. Moltling;.—Arches are often decorated with moreor less elaborately dressed stone, known as label and soffitmoldings. The former is sometimes cut in the ring stones,but oftener forms a separate course of thin stone. If such 8 MASONRY. 61 is the case, the stability of the arch should not depend onthe strength of the stone in the molding-. The soffit molding is frequently in the form of a bead andcone, or three-quarter round and cone, or some similarshape. Entrance arches are often decorated with variousdevices cut in the soffits, especially in entrances to cathe-drals, public and office buildings, etc. In Fig. Gl, the label mold is shown at a\ the arch rings,. Fig. 61. at b and c\ the soffit mold, at c\ the brick backing, or filling,at d\ and the voussoir joints, at g. Every alternate pair ofvoussoirs should be tied together with galvanized-ironclamps doweled into the stones, as shown at/l 110. Centers.—In building an arch, it is carried upfrom both piers or abutments at the same time. Duringconstruction, the stones must be supported until the ring iscompleted. For this purpose, a framework, made of plankshaving one side cut to exactly fit the curve of the arch, isused. This framing, known as a center^ is supported onposts; it is usual to insert wedges between the center fra-ming and the posts supporting it, which, when the arch is 62 MASONRY. 8 completed and the mortar has set, are driven out gradually,so as to bring the load on the arch ring without shock. Thecenter should be strong enough to support the weight ofthe arch and a share of the wall above, as no weight should beput on the
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