Our eastern shore affords sufficient proof that the ocean has both receded and advanced recently—at least recently in comparison with the great changes which have occurred to modify the surface of the earth. In proof of this recession, we have the upper _carses_, or deltas, visible in every firth or creek where a river falls into the German Sea. These carses, on the firths in Ross-shire, at Dun near Montrose, around the upper end of the Firths of Tay and Forth, are all of nearly equal level, about 20 feet above the highest stream-tides. The gravel bar at Montrose is considerably above the present sea-level. A number of caves exist on this {290} eastern coast, evidently worn into the rock by the action of the sea at the height where the waves have broken. These caves have nearly one level, corresponding in height with that of the carses. There are also many places where the coast has been shorn away by the action of the waves, and a shelf of rocks left extending out some hundred paces. This abrasion, which takes place nearly at, or a little above, low water-mark, is effected by innumerable hard pebbles (the most indurated parts of the rocks which give way being converted into battering material for further reduction), being upborne and dashed against the rock by the continuous heaving and lashing of the waves. Wherever any breach commences from the feebler opposition of any softer part, the action of the waves and battering train proceeds with increased impetus and concentration, especially if the breach be wedge-shaped narrowing inward, thence caves of considerable extent are hallowed out. The rocks thus abraded and undermined, tumble down and are ground into sand, which is swept by the tides and motion of the waters into the depths of the ocean, or borne along to the upper end of the bays, or to some part of the coast where more sluggish lateral tides, and particular motion of the waves leave it and throw it ashore to be blown up into {291} downs. There are some former islands which have been altogether shorn down to this sea-level, of which the Bell-Rock, extending nearly a mile of shelf, affords a well known specimen. In many places of the coast, these shelves accord with the superior former level of the sea, and with the floors of the caves.