CHAPTER III 



FIXATION OF SHIFTING SANDS AND OF UNSTABLE SLOPES 



Shifting sands may be divided into two classes, viz. 

 coast- and inla?id-dunes, the first being caused by 

 sand thrown up by the sea and blown inland by the 

 wind, while the others are caused by the disintegration 

 of soft sandstone rocks by torrential rains and wind, or 

 by wind alone. These are also driven forward by the 

 prevailing winds and form billows of sand, which, in 

 advancing, often cover wide extents of country, drifting 

 even over the tops of well-marked hill ranges. 



The best-known example of coast-dunes are the 

 Dunes of Gascony, stretching from Arcachon to near 

 Bayonne, and which, thanks to the genius of Bremontier, 

 who started the work at the close of the eighteenth 

 century, have been consolidated and turned into forests 

 of Pinus maritima. Of inland-dunes, those of the 

 Sahara and its extensions into the Libyan and Nubian 

 deserts are the best-known examples. 



In the Tropics littoral dunes are not usually, if at 

 all, as extensive as those of Gascony. There have been 

 cases, however, as near Madras and near the mouths 

 of the Indus near Kurraclii, where wind-driven sands 

 have been a source of danger. The sand-drifts have 

 been checked by the planting of sand-binding plants. 

 Near Madras plantations of Casuarina have effected 

 this, with the help of other sand-binding plants which 

 have the faculty of giving out a network of prostrate 

 branches or underground creeping rhizomes, which 



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