The outline of the curve of a valley's sides ultimately depends on the angle of repose of the detritus which covers them, if there has been no subsequent change, such as the passage of a glacier along the v.alley, which tends to destroy the regularity of the crosssection.
For this reason X is also known as the angle of repose.
The condition of stability is that this obliquity shall not exceed the angle of repose of the earth.
The total pressure exerted between the rubbing surfaces is the resultant of the normal pressure and of the friction, and its obliquity, or inclination to the common perpendicular of the surfaces, is the angle of repose formerly mentioned in 14, whose tangent is the coefficient of friction.
The angle made by the sides of the cones with the axis should not be less than the angle of repose.
