A primary consideration to which it is needful to direct attention consists in the due appreciation of the fact that the land and not the sea is to be here credited with the action under discussion. When a considerable part of a coast-line formerly existing above tide-marks is found to gradually sink below the sea-level, the observer is probably apt to assume that the sea has simply altered its level. The idea of the sea being a constantly changing body is so widely entertained, and that of the land being a solid and immovable portion of the constitution of the earth, is also so deeply rooted in the popular mind, that it may take some little thinking to throw on the land the burden of the change and alteration. It is nevertheless a fact that the great body of water we name the ocean in reality obeys the laws we see exemplified in the disposition of the water contained in a cup or bowl. The water of the sea thus maintains the same level, and is no more subject to violent and permanent alterations than is the water in the cup or bowl. Hence when part of a coast-line appears to become submerged, we must credit the land with being the seat of the change, seeing that the sea must be regarded as stable, unless indeed it could be shewn that the level of the sea had undergone a similar change on all the coasts it touches. Thus if the southern coast of England were found to have been depressed say to the extent of six feet, we must credit the land with the change, unless we could shew that the sea-level on the opposite or French coast had also changed. Now the alterations of land are mostly local or confined to limited areas, and are not seen in other lands bounded by the same sea or ocean as the altered portion. Hence that the land must be regarded as the unstable and the sea as the stable element, has come to be regarded as a fundamental axiom of geology.