932 



THE NATURE BOOK 



dunes are the configuration of the sur- 

 face of the shore, the nature of the rocks 

 along the coast, the set of the tide, and 

 the direction of the most prevalent winds. 

 Indeed, the prevaihng wind plays a very 

 important part, for if it be one that blows 

 on-shore, it dries and blows the sand left 

 exposed by the receding tide inland ; 

 while a prevaihng off-shore wind will blow 

 the sand back into the sea, and so prevent 

 the formation of sand-dunes. 



The sand-dunes generally form a kind 

 of natural embankment, separating the 

 comparatively low ground inland from 

 the shore proper. Very often this low 

 land, from which the sea has been 

 gradually shut out by the development 

 of the sand-dunes, forms at first a brackish 

 lagoon which, owing to the growth of 

 aquatic vegetation, gradually becomes 

 converted into a marsh ; and this marsh- 

 land is in turn slowly raised by the growth 

 and decay of the water plants, until it 

 eventually becomes drained, and forms an 

 area of land capable of growing and yield- 

 ing a rich harvest of corn. 



The shore and land between Poole and 

 Studland afford an excellent opportunity 

 for the observation of this most interesting 



process by which Dame Nature reclaims 

 the land from the sea. During the spring 

 tides, if we visit this stretch of the coast, 

 we shall see a wide expanse of flat shore 

 composed of beautiful firm sands. A 

 soft, steady wind is blowing in-shore, 

 and, helped by the hot rays of the sun, 

 is rapidly drying the surface of the shore 

 that has been left by the ebbing tide, 

 and soon begins to drive the dried particles 

 of sand landwards. 



The shore slopes very gently upwards, 

 and the drifting sand, as it is blown land- 

 wards, first passes over a perfectly smooth 

 area up the slope until it comes to the 

 inland margin of the shore, where the 

 surface becomes more or less uneven, and 

 is partially clothed by a scanty vegeta- 

 tion of sedges and grasses, and other plants. 

 There, unless the wind is blowing a gale, 

 the sand becomes heaped up amongst the 

 stems of the grasses, and gradually, like 

 drifting snow, fills up all the uneven 

 depressions. Quite a superficial examina- 

 tion of many of the plants that grow 

 along the inland sandy margin of the 

 shore, comprising chiefly certain species 

 of grasses, sedges, and the like, will reveal 

 the fact that they are specially adapted 



RF:EDS and grass arrest the progress of TliL. SAND. 



