192 SEA AND LAND 



would lodge, and if the storm were long continued the sands 

 might be built up to a sufficient height for the ridge to emerge 

 above the level of the sea and form a beach. Unless this 

 emergence of the crest were effected, the succeeding storms 

 of lesser energy would tend to destroy the imperfect barrier 

 by sweeping waves over its crest without breaking, in which 

 case, as will be readily perceived without further explanation, 

 they would tend gradually to scour away the elevation, dis- 

 tributing the sand between its position and the neighboring 

 shore. The shallowing of the water thus brought about 

 might go on by the successive temporary formation and 

 distribution of submarine sand reefs, until finally, in some 

 great storm, a ridge was built up of considerable length, 

 perhaps along a great distance of shore, which rose above the 

 level of ordinary low tide. When such a ridge had been so 

 formed, high enough to escape the scouring action of waves 

 of any considerable magnitude, operating by overrunning its 

 top, each succeeding storm, even those of ordinary energy, 

 would tend to add to the mass by bringing in more sand from 

 the continental shelf. 



As will be noted hereafter, the Inner portion of the 

 continental shelf, the part which lies in shallow water next 

 the shore, commonly receives considerable contributions 

 of sand, which work along the coast from regions beyond 

 the limit of the barrier reefs. Thus on our Atlantic coast 

 a good deal of arenaceous material may have journeyed 

 from as far north as New Jersey, where it was contributed 

 to the sea during the last glacial period, or washed into the 

 ocean from deposits of sandy matter formed during the ice 

 time. In this way the waves can continually bring in sandy 

 matter without diminishing the depth of water on the out- 



