CLAY SOILS, especially the yellow clay; illustrated by the notable slip at New Cross, near London, when some 90,000 cubic yards of yellow clay moved upon the smooth surface of a shaly clay bed and covered the formation: also the brown, and boulder clay, and the lias clays, as witness the well-known recorded slips in the Midland counties of England, in which either aluminous or calcareous material may preponderate. There are few, if any, earths in which the cohesion, weight-sustaining power and ability to resist the action of water and meteorological influences are practically the same at all depths, the different conditions, arrangement, and character in which they are found being almost infinite, and there are earths which may become consolidated and watertight if in a constantly moist and protected state, that when dry and exposed will shrink, fissure, and soon become unstable. Consequent upon cohesion, a cutting may stand for some time almost vertically; nevertheless stability cannot be considered as solely regulated by the cohesion of earth, for an embankment of gravel, sand, or broken rock with a proper slope and protected from erosion will usually safely bear more load than an embankment of clay, although the former material may be said to have no cohesion; but the lateral thrust of dry, firm sand is known to be small, provided the sand is not disturbed; also no earth can be said to be immovable under every condition, but consideration of the soils particularly liable to disturbance or mutation is, under ordinary circumstances, the main question to be determined.