At the base of the upper 30 feet, 1½ to 1 slopes, about 1 ton per square foot. At the base of the middle 30 feet, 2 to 1 slopes, about 1¾ ton per square foot. At the base of the lower 30 feet, 3 to 1 slopes, about 2¼ tons per square foot. NOTE.—The actual strain is probably approximate to a mean between the two values, and is nearer the latter than the former. There is no reason why the varying slope system should not be adopted in embankments of clay or soil having considerable powers of cohesion, as the expense of trimming the slopes is very little more than making them to a straight line. To trim a slope to an elliptical, parabolic, or cycloidal curve would be a needless refinement requiring a template; moreover, the surface is better when it consists of straight lines, provided that at the junction of any two inclinations the point of meeting is sufficiently rounded to prevent a lodgment of water. In cuttings in non-weathering tenacious soil the upper part might be left at a steep slope for 5 or 6 feet from the surface of the ground. It is evident that the depth of a cutting or the height of an embankment affects the stability of the slopes, but some soils are so weak that an embankment of even little height will not be at rest until the toe of the slope is supported. If the slopes were not pressed out the earth in the central portion of an embankment would stand at any weight less than that which would crush it when in its weakest condition; therefore, as the load increases downwards it is a logical deduction that the slope should be flatter as it approaches the base. In slips the form generally assumed in soils having considerable cohesive power nearly approaches that of a parabolic curve, which shows that a straight slope is not the correct one in tenacious soil, and theory confirms it. In the case of cuttings of considerable depth, apart from the question of the best form of slope, in order to lessen the velocity of the surface water and the extent of a slip, and cause supported weight upon the slopes, they can be divided by broad terraces or benchings, about 6 feet in width, and at vertical distances of 15 to 20 feet, upon which can be impermeable catchwater drains. It is important not to allow a flow in a straight line or nearly so, as the velocity of the water may erode the slope. If the nature of the earth and its resistance to erosion will allow, the benches or steps should be abrupt, in order to cause the greatest resistance and deviation from a direct discharge. The slopes of the catchwater drains may require to be covered in a flood district or one having a heavy rain or snowfall.—_Vide_ Chapter IV.