2016. Brick, stone, or mud walls, consist of three parts; the foundation, the body of the wall, and the coping. The foundation should he somewhat broader than the body of the wall, and of depth proportionate to the quality of the subsoil or intended plan of culture. In some cases, where it is intended that the roots should have free access to both sides of the wall, it should be placed on arches or piers, with plank-stones, the soffit of the stone or under crown of the arch being within 6 in. or 1 ft. of the surface; and the openings smaller or larger, according to the power of the materials to resist the pressure of the wall. The arch should be a segment of a circle, or an ellipsis, and the piers proportioned to the qualities of the foundation and the superstructure.