With regard to the inclination and the form of a slope, and the prevention of slips in earthwork, in any slip the surface must be affected; therefore, to determine the slope of permanent stability of any earth, whether in a cutting or an embankment, is of great importance. An unnecessarily flat slope is not only a monetary waste but may be a cause of instability, for it exposes a larger surface to deterioration by the weather. By what means is a correct decision to be attained? Experience has shown that certain earths under known conditions will repose at particular inclinations; however, to empirically assume that any earth will always stand under any circumstances is clearly imprudent and untenable. As a guide, a table of slopes for earths is valuable, but consideration of the consequences of movement, and the distinctive features of each case should govern a decision. Should the earth be treacherous and require a flat slope, it may be advisable to reduce the quantity of excavation by the erection of a retaining wall, not only to effect a saving in expenditure, but also to permanently support the soil, and prevent instability. An inspection of neighbouring quarries and the waste tips, sand or gravel pits, hills and cliffs, cuttings and embankments for roads, river banks, &c., will afford an indication of any local peculiarities caused by the climate or otherwise; and a comparison of the natural slopes assumed when the soil has to withstand vibration, and when not so disturbed, will enable a judgment to be formed of its deleterious effect upon the earth; but above all, an examination of the cuttings and embankments passing through or upon the same geological formation. Reliable evidence can be so obtained upon which the slope of permanent repose can be determined according to the dictates of science and experience, but the probable consequences of instability will demand a due regard to provision against contingent deteriorating influences which may almost destroy cohesion and render it necessary to rely solely upon frictional resistance, the remaining resisting power against movement of the earth, except in solid rock, which may stand with an overhanging or vertical face, whereas mud and quicksand may not be in a state of rest even when horizontal.