SAND DUNES 



October 23, 1910, to March 5, 1911, the dune 

 advanced 256 inches, or at the rate of about 

 60 inches a month. The pine-grove dune ad- 

 vanced only 3 inches in the summer of 1910 

 from May 15 to November 6, but in the stormy 

 weeks between the latter date and March 5, 

 1911, it advanced 71 inches. 



On January 29, 1911, the signal stake placed 

 by the Coast and Geodetic Survey on a high 

 dune near the beach was 175 inches due south 

 from the retreating northerly face of the dune. 

 After four windy months, on May 28, the stake 

 was only 132 inches from the edge,— 43 inches 

 had been cut away. 



In a recent book on the Sahara, Hanns 

 Vischer describes similar dunes, but on a 

 much larger scale. He says: '' Gradually these 

 dunes are piled up and form ridge after ridge, 

 some of them over four hundred feet high. 

 These rise from the north in soft curves to 

 fall off on the other side like a mighty wave. 

 The ceaseless wind, mostly from the north- 

 east, moves the sand along the surface, con- 

 tinually changing the position and formation 

 of these banks." His photographs show dunes 

 entirely devoid of binding vegetation, with 

 camels walking on the hard windward sur- 



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