It is probable that the coarser soils, permitting more rapid percolation, would generally give higher results.
The resistance of clay to percolation by water depends chiefly upon the density of the clay, while that density is rapidly reduced if the clay is permitted to absorb water.
But in order that the action may be complete the initial resistance to percolation of water at every part of the soil must be such that the motion of the water through it shall be insufficient to disturb the water-borne mineral and organic particles lodged on the surface or in the interstices of the soil.
The percolation will then be very small, and the risk of disintegration will be reduced to a minimum.
Thus, if there is any percolation between the Mediterranean and the Dead Sea, it must be towards the latter.