Each earth requires to be duly considered; for instance, gravel and sand are pieces of rock, however small, and for earthwork purposes the particles may be regarded as insoluble in water; nevertheless in the case of sand, should it be charged with water, it may be necessary to treat it as a fluid, the same as mud, although water does not change the particles; however, slips in cuttings and embankments in sandy or gravelly soils are not usually caused by their becoming gradually saturated throughout their mass, but by a flow of water which creates water seams: the stability, therefore, is dependent upon equal percolation and drainage and protection of the surface; and the slope that should be given to a sand cutting is also governed by the quantity of water it will have to hold, and whether the sand is pure or loamy. The depth of a cutting in sand has a considerable influence upon the slope of stability, for frequently sand is in a dry state in the upper portion of a cutting, but beneath it is wet, and partakes more of a silty character, and therefore may stand at a steeper inclination in the upper part, but require a flat slope in the lower portion. The same conditions are found in all soils, and the sides of a cutting vary, one may be comparatively compact and free from water, the other in a wet state and disintegrated. They will not permanently repose at the same angle, the slope varying according to the degree of dryness, size, and uniformity of the particles. In all earths in which cohesion is liable to be quickly destroyed, a straight slope is the best as having an even surface, which prevents the formation of depressions and causes the water to drain away, and also offers the least surface to the weather. In all earth such as shingle, gravel, or sand, consisting of pieces of rock or rubble, or having round particles, it is important to remember that any surface disturbance may cause serious movement, particularly should it commence at the bottom of a slope, as then the revolving action may not cease until a flatter inclination is produced by material rolling from the top and not reposing until it nearly reaches the base. The quantity of moisture is the chief governing condition of the slope of repose in clay soils, and it should not be forgotten that this may vary considerably. Clay when only slightly moist may stand at a 1 to 1 or 1½ to 1 slope, but as it gradually becomes in a wet state will require a flatter inclination, and may not be at rest until the slope is at least 3 to 1, and it is not safe to rely upon a steeper slope than 3 to 1 in the case of almost any surface clay beds liable to become charged with water, and even 4 to 1, should the excavation be on the side of a clay hill and near houses, or the ground be loaded; but clay having some powers of cohesion which usually are greater as the clay is harder, is not so quickly disintegrated as in the case of more porous