The majority of geological formations have certainly been deposited in what was at their respective periods the sea; but Sir Charles Lyell, Prof. Geikie and others have shown that the action of the waves and currents upon sea-cliffs, and their power to remove matter from above to below the sea-level, is very insignificant compared with that effected by atmospheric agents, by rain and rivers, in the interior, in consequence of the immensely more extended area upon which these act; so that, even supposing the height of ancient cliffs to have been very much greater than those of the present time which have been considered to average not more than twenty-five feet, it appears difficult or rather impossible to attribute the origin of the materials of which they consist, sometimes amounting to several miles in thickness, to the erosion of coast-lines, with the exception of a comparatively thin stratum situated at their base. Those who have ascribed their origin to marine denudation have given no satisfactory explanation of the manner in which the débris from the disintegration of the cliffs has been redistributed to form these strata.