As time passed, more and more sand would be thus deposited, the ground probably sinking and the weight of sand increasing, until the lower layers had stiffened into rock. In after days a slow upheaval of the ground came about, and where ocean waters had flowed would be dry land. By-and-by--who can say how long after?--the ripple-marked slabs of sandstone, petrified memorials of the past, would be found; perhaps far inland, if the country had risen much; perhaps in a quarry by a young Scotch working-lad, to be marvelled over as a specimen of old Ocean’s bygone work. Another such token of the past is found in hardened raindrop traces, impressed on solid sandstone. The rain fell on a soft sandy shore, making tiny holes in the sand, with splashed-up ridges round each small hole. Have we not all seen this? If not, we might have used our eyes better. Before the coming in of the next tide the surface hardened, like the sand-ridges already described, and so, being covered over by new layers of sand and gradually transformed into rock, it was later uplifted above the sea, and the holes have lasted intact until now. It may be objected that the time between one high tide and another is hardly long enough for any such hardening process--even on the hottest and driest of summer days. Then the hardening may have taken place only on that slender belt of sand, which is covered for a day or two by the spring tides, and is not again reached by ocean-waves for nearly a fortnight. In earlier chapters it was shown--first, how the Ocean is ever striving to keep a level surface; and secondly, how the object sought is never attained to. Not only are the waters in ceaseless motion, heaving to and fro under the influence of every passing breeze, borne hither and thither by mighty streams, disturbed by innumerable storms. But also the powerful attraction of the land, particularly of great mountain ranges, lifts the sea-surface in some regions hundreds of feet higher than in others. So that a ship, passing from the neighbourhood of a mountainous coast to mid-ocean, may be actually sailing or steaming downhill, actually descending a vast gentle watery slope. Another question as to Ocean’s level has much exercised the minds of men. Throughout the world, remains of sea-creatures in countless multitudes are found embedded in the substance of water-built rocks: sometimes the very rocks being made up of them. This, not only on the tops of lesser hills, but at the summits of mountains eight thousand feet high, twelve thousand feet high, sixteen or eighteen thousand feet high. Very ancient remains they often are, certainly many tens of thousands of years old. But whatever their age may be, they echo and add to the story which is told by the rocks themselves.