In the erection of brick walls, especial care should be given to the construction of arches which will be necessary to span the openings. Arches, in general, should be laid in cement mortar. The two principal forms of arch in brickwork are the rowlock arch, where the bricks are laid in concentric rings of headers, Fig. 114, and the gauged arch, where the bricks are cut and bonded on radial lines, as in Fig. 115. For arches of large spans the bricks are often laid in rings of stretchers, Fig. 116, and, if the span is very large, these may be strengthened by bonding in headers as in Fig. 117. An important point in the use of arches is to see that each abutment contains sufficient masonry to support the thrust of the arch; tie rods should be freely used in case of any doubt, and arches of large span should be sprung from stone skewbacks carefully cut to radial lines, as in Fig. 118.

Fie. 114. Rowlock Arch.

Fie. 114. Rowlock Arch.

Fig. 115. Gauged Arch.

Fig. 115. Gauged Arch.