When the bulk of the material has been taken out of an earth or clay cutting, the work of trimming the slopes should be put in hand, so that any surplus left on the wings, or sides, may be removed, and carried away before stopping the earth-waggons. The angle of slope having been decided, a battering rule of light wooden boards is made to correspond to the slope, and in form similar to that shown in Fig. 64. A plumb-bob is suspended from a fixed point, A; the lower end, B, is then held against a peg or mark which indicates the correct level and width of the cutting at the place, and the upper end, C, is raised or lowered until the plumb-bob string coincides with the vertical line marked on the rule from A to D, and the plumb-bob rests steadily in the space cut for it at D. With this battering rule a length of seven or eight feet, according to the size of the rule, is first trimmed to the correct slope, and by continuing the application of the rule up the side, a correct slope line is obtained from bottom to top of slope at that place. By repeating the process at convenient distances along the cutting, a series of correct slope lines are obtained, and the intermediate space can readily be trimmed to correspond. The same form of battering rule and method of working is applicable for trimming the slopes of the embankments. When the slopes of the cuttings and embankments have been trimmed, vegetable soil, which has been laid aside, or reserved as previously described, should then be spread evenly over the slopes to the uniform thickness of not less than four inches, and the whole sown with good grass seeds to form a strong sward. The trimming, soiling, and sowing of the slopes not only gives a more finished appearance to the earthworks, but the strong grass, when once well grown, binds the surface together, and helps to resist the injurious effects of heavy rains and melting snow. There are many places abroad where a neat finish to the earthworks is considered quite a secondary matter, or where it would be difficult to obtain suitable soil to spread on the slopes. The earthworks are hurried forward to allow the iron highway to be laid down as quickly as possible, the slopes of the cuttings and embankments are only roughly trimmed, and nature is left to supply such grass or vegetation 73 as may spring up, or be self-sown.