SAND DUNES 



for its steep crest is borne in front, while the 

 long, sweeping side is left behind or to wind- 

 ward. In these respects it is but the mag- 

 nification of the ripple-marks on the sur- 

 face. 



There are at the present time two very 

 striking examples of this form of dune at Ips- 

 wich, one of which, like a devastating tidal 

 wave, is overwhelming the southernmost of 

 the pitch-pine woods, while the other, nearer 

 the mouth of the Essex River, is burying in 

 its progress a grove of white birches. Both 

 of these are improtected on the north for a 

 considerable distance either by bushes or by 

 grass, and Boreas rushes over them unim- 

 peded. The northerly sloj^e is hard and finnly 

 packed, and extends gently upward at an 

 average angle of nine degrees, whereas on the 

 south the sand, freed from the mighty power, 

 settles softly at an angle of rest generally as 

 steep as thirty-two degrees. Here it is so 

 loosely compacted that one may easily sink 

 half-way to the knees. 



Both of these dunes have crests higher than 

 their victims, the trees. The pine grove has 

 been so far imbedded that the remains of the 

 buried trees are beginning to reappear on the 



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