56 SEA AND LAND 



pieces, and the pebble enters the mill where so many of its 

 fellows have met their fate. The close observer after a storm 

 may find any number of these bowlders along a pebbly shore 

 which still show a trace of the sea-weeds which bore them 

 to the coast. Wading out to near the breakers, he can often 

 see these sea-weeds with their attached pebbles — sometimes 

 as large as a man's head — poised in the wave the moment 

 when it rises for the overturning which makes the surf. On 

 a (quarter of a mile of the Marblchead beach I have estimated 

 that as much as ten tons of these seaweed-borne pebbles 

 cam.: ashore in a single storm. Many of the beaches, which 

 are so inadequately provided with pebbles from the neighbor- 

 in^ shores" where the waves are attacking/ the firm land that 

 they could not be maintained from that source alone, are 

 sufficiently fed by the means of supply afforded through the 

 action of marine |)lants.'^* 



It follows, from what has been above said, that the move- 

 ment of coastal detritus is easily accomplished on straight 

 beaches, such as are characteristic of the southern portion of 

 the United States, but is very limited in amount on the rock- 

 bordered shores. Thus, while on the coast of Maine wave- 

 w^orn pebbles are rarely carried for a distance of more than a 



* On the parts of the shore where the land has I)een extensively occupied by 

 summer residents, the owners have in many cases protected the coast trom erosion 

 by embankments and sea-walls, thus diminishing the amount of dclwis which was 

 formerly contributed to the pocket-beaches. In these artificial conditions the 

 beaches often wear out, and the sea begins to assail the part of the coast which was 

 once well protected. In sucli cases the only way in which the erosion can effec- 

 tively be corrected is by carting each year to the beach a sufficient quantity of 

 large bowlders to give employment to the waves and prevent their encroachment 

 upon the shore. The larger these bowlders, the better ; for if they are of small size 

 they will be tossed about by slight storms and rapidly wear out, while masses 

 weighing half a ton will be stirred only by the more tumultuous seas. 



