73 8 THE POPULAR SCIENCE MONTHLY. 



in width, and bearing the mossy Hudsonia or scrubby bushes of 

 beach plum and wax-myrtle, or in some places, especially on the 

 outer row of dunes, only supporting a meager growth of beach 

 grass. Frequently, between two rows of dunes, an expanse of 

 salt meadow occurs, or a sand flat bearing stunted forms of 

 plant life. With this third division ends the domain of vegeta- 

 tion, succeeded by the sloping strand upon which the tide rises 

 and falls. The sand-bar, exposed at low water at the extremity 

 of the beach, is constantly increased in length and height by the 

 action of the currents, and the process of beach formation is 

 here continually in progress. 



As the tide falls, the sand laid bare is rapidly dried by the 

 wind and carried above high- water mark. Then, safe beyond the 

 reach of the waves, the minute particles are borne still farther 

 from the water, and striking against some piece of drift-wood, 

 bush, or tuft of grass, quickly build a hillock, which grows larger 

 and larger as more sand falls upon it, and a dune is formed many 

 feet in height. The material of which these dunes are composed 

 is never at rest, but flies hither and thither with the wind, and a 

 hillock ten or fifteen feet high to-day may noiselessly be taken 

 down to-morrow and rebuilt a hundred yards away. In time, as the 

 beach grows seaward and the dunes increase in number, those of 

 earlier formation, which are somewhat protected from the breeze,, 

 catch a few seeds, and tufts of grass begin to grow upon them. 

 Still later, the mossy Hudsonia or some starveling wax-myrtle 

 finds a little sustenance, and as years elapse the dunes become so 

 thickly covered with vegetation that under the protection of the 

 seaward hillocks they retain their form with comparatively little 

 change. 



Thus have the beaches grown. First a sand flat built by ocean 

 waves and currents ; then a series of low, shifting dunes ; next 

 sheltered hillocks, on which grasses and shrubs fasten their pro- 

 tecting roots ; succeeding the latter a growth of small cedars and 

 pines ; and, finally, as centuries roll on, majestic forest trees raise 

 their spreading tops and shelter a dense undergrowth. 



These few words suffice to describe the beaches' growth, their 

 physiology ; but many pages might be written upon their history, 

 the details of their development, their changes and their decay. 

 Unfortunately, the records are but incomplete. From the memo- 

 ries of old men we can glean some facts in regard to the former 

 condition and extent of certain beaches and concerning marked 

 changes in them which have been notable events to men of quiet 

 lives. In a few instances, surveys were made a century or two 

 ago which can be compared with those of to-day. At present we 

 can watch the changes which occur from year to year. As geo- 

 logical science advances we can speculate concerning the past on 



