Ledges. A ledge never should be allowed to run through the cellar wall, as water will seep into the cellar through minute crevices in the rock; it should always be cut off, and the cellar wall built inside of it, as shown in Fig. 4. An open tile drain should be laid below the level of the cellar floor to carry away the water in the ground, as shown at a. This drain should be connected with the sewer by a trap outside the foundation wall, or if in an isolated district where there is no sewer, it should be carried to the nearest available spot giving sufficient pitch to allow the water to run off. If a ledge comes through the cellar floor, water may enter, as the moisture in the ground outside will force its way up through it. To prevent this, the floor should be dug away, and a Portland cement floor laid above it. (See Topic 8.)