Page:Popular Science Monthly Volume 66.djvu/409

Rh chief constituents being fragments of shells, serpula tubes and corallines. There are no such stratified subaqueous rocks as are found in this country, but everywhere the cut edges of the rocks show the peculiar sinuous lines that characterize the stratification of drifting sands. Most—if not all—of the harder rocks are doubtless the result of the action of water and air on these aeolian masses. At almost every point where the action of the sea is traceable it has resulted either in cementing together the layers of these rocks till all evidence of stratification is

lost, or else its mechanical effect has been more immediate than its chemical, and the rock has crumbled into its constituent grains and has become once more a sandy beach, in turn yielding up its substance to build the present sand dunes of the coast, which have the same æolian structure as their predecessors.

The mechanical action of the sea operating on the already hardened rocks has left them carved in the most fantastic shape (Figs. 8, 9), and with edges so sharp that it is almost impossible to walk upon them. In many places the rocks are honeycombed through the action of water, and subterranean passages connect inland waters with the sea. Caves, too, sometimes of considerable extent, are found at various places, especially