[Illustration: Fig. 34 - SECTIONAL VIEW OF JOINT.] Fig. 34 - SECTIONAL VIEW OF JOINT. *Silt-Basins* should be used at all points where a drain, after running for any considerable distance at a certain rate of fall, changes to a less rapid fall,—unless, indeed, the diminished fall be still sufficiently great for the removal of silty matters, (say two feet or more in a hundred). They may be made in any manner which will secure a stoppage of the direct current, and afford room below the floor of the tile for the deposit of the silt which the water has carried in suspension; and they may be of any suitable material;—even a sound flour barrel will serve a pretty good purpose for many years. The most complete form of basin is that represented in Figure 24. [Illustration: Fig. 35 - SQUARE BRICK SILT-BASIN.] Fig. 35 - SQUARE BRICK SILT-BASIN. When the object is only to afford room for the collection of the silt of a considerable length of drain, and it is not thought worth while to keep open a communication with the surface, for purposes of inspection, a square box of brick work, (Fig. 35,) having a depth of one and a half or two feet below the floor of the drain,—tiles for the drains being built in the walls, and the top covered with a broad stone,—will answer very well. [Illustration: Fig. 36 - SILT-BASIN OF VITRIFIED PIPE.] Fig. 36 - SILT-BASIN OF VITRIFIED PIPE. A good sort of basin, to reach to the surface of the ground, may be made of large, vitrified drain pipes,—such as are used for town sewerage,—having a diameter of from six to twelve inches, according to the requirements of the work. This basin is shown in Figure 36. Figure 37 represents a basin made of a 6-inch tile,—similar to that described on page 130, for turning a short corner. A larger basin of the same size, cheaper than if built of brick, may be made by using a large vitrified drain pipe in the place of the one shown in the cut. These vitrified pipes may be perforated in the manner described for the common tile. [Illustration: Fig. 37 - TILE SILT-BASIN.] Fig. 37 - TILE SILT-BASIN. In laying the main line _C_, (Fig. 21,) an underground basin of brick work, (Fig. 35,) or its equivalent, should be placed at stake 7, because at that point the water, which has been flowing on an inclination of 1.09, 2.00 and 2.83 per 100, continues its course over the much less fall of only 0.56 per 100.