Brick walls in exposed situations are often treated with some substance to render them waterproof. One of the most successful processes is known as "Sylvester's Process," and consists in applying two washes to the walls, one composed of Castile soap and water, and the other of alum and water. These applied alternately will generally render the work impervious. Several patented solutions are now upon the market, each of which is warranted to protect against moisture.

Fig. 120. Wooden Lintel.

Fig. 120. Wooden Lintel.

Fig. 121, Relieving Arch.

Fig. 121, Relieving Arch.