SAND DUNES 



to leeward. Owing to the multitude of inter- 

 lacing rootstocks and rootlets of the beach 

 grass the crest sometimes overhangs like a 

 breaking wave, and masses of roots and sand 

 fall from time to time as the wind undercuts 

 them. Indeed, this slope of the dune, the re- 

 verse of the normal one about to be described, 

 is, I believe, due entirely to these beach grass 

 roots— bricks made with straw. 



These reversed waves of sand reach their 

 fullest development at the southern end of 

 the Ipswich dunes, where they form a series 

 of parallel ridges, with their steep sides facing 

 the north. They have advanced southward in 

 the middle more than at either end, so that 

 they describe the arcs of circles, and resemble 

 a series of gigantic amphitheatres. One wave 

 that I measured in 1903 could easily be traced 

 for some 1,350 paces, or three-quarters of a 

 mile, and it stretched from the estuary on the 

 inside to the sea on the outside. Its breadth 

 varied from forty to two hundred yards, and 

 its height from twenty to fifty feet. The 

 distance between the waves varies from 

 a hundred yards to a quarter or half a 

 mile. 



The highest points or peaks of the dunes 



17 



