, then, undoubtedly, the mass,
, will move to the left, because there is an unbalanced force,
, to cause the motion.
The vertical height of an unsupported bank, where vertical cracks occur of depth
, will then be that given by [Equation (8)], which is one-half the value usually given. This is generally an extreme lower value; for any earth endowed with much cohesion must be capable of exerting tension. If the tension exerted is sufficient to drag down
(which can stand unsupported), that is, if the wedge,