It is a general observation among mariners, that a high coast and rocky shore have deep water; whereas a low coast, and sandy shore, are as naturally attended with shallow water.  The explanation of this fact will appear by considering, that a steep rocky coast is occasioned by the sea having worn away the land; and, when that is the case, we are not to expect sand should be accumulated upon that shore, so as to make the sea shallow.  Look round all the coasts of Great Britain and Ireland that are exposed to the wide ocean, as likewise those of France and Norway, deep water, and a worn coast, are universally to be acknowledged.  If again the coast is shallow, this is a proof that the land affords more materials than the sea can carry away; consequently, instead of being impaired, the coast may here increase and be protruded from the land.  Such is the case in many places along the coast of North America, where several reasons concur in accumulating sand upon that coast; for, not only is the shore plentifully provided with sand from the rivers of that continent, but also the sand of the Mexican Gulf would appear to be carried along this coast with the stream which flows here towards the north, and which has thus contributed to form the banks of Newfoundland.

The second general observation is to be considered as respecting the shape of coasts, in like manner as the first had in view their elevations.  Now, it is plain that the shape of the coast, in any part of the land, must depend upon a combination of two different causes.  The first of these is the composition of the land or solid parts of the coast; if this be uniform and regular, so will be the shape of the coast; if it is irregular and mixed, consisting of parts of very different degrees of hardness and resistance to the wasting operations, the coast will then be, cet. par. irregular and indented.  The second, again, respects the wearing power.  If this wearing power shall be supposed to be equally applied to all the coast; and, if every part of that coast were of an equal quality or resisting power, no explanation could be given, from the present state of things, for the particular shape of that coast, which ought then to be wasted in an equable manner by the sea.  But neither is the coast, of any extensive country at least, composed of such uniform materials; nor is the application of the wearing power to the coast an equal thing; and this will form the subject of another observation.  The third general observation, therefore, regards the operations of the sea upon the coast, and the effects which may be perceived in consequence of that cause, independent of the qualities of the coast, or supposing them in general to be alike.  Here, according to the theory, we should expect to find deep water and an indented coast upon a country, in proportion as that coast is exposed to the violence of the sea, or is open directly to the ocean.  We have but to look along the west coast of Norway, the north-west of Scotland, the west of Ireland, and the south-west of England and of France; and we shall soon be convinced that the sea has made ravages upon those coasts in proportion to its power, and has left them in a shape corresponding to the composition of the land, in destroying the softer, and leaving the harder parts[14].