OP MABINE COASTS. 



69 



S'an Francisco is situated the beautiful Golden Gate Park, a result of 

 successful reclamation operations, but south of the park there is still an 

 extensive area, where the drift sand is blown about by the winds. 



The shore is open to the Pacific and the waves break furiouslj' on 

 the sand. After a strip of gently sloping beach, about 25 m. wide, 

 follows a well developed littoral dune, and inside of this there is a de- 

 pression, the bottom of which is sometimes level and drj', in other 

 places occupied by small pools of stagnant water. Further inland, 

 small mounds of sand, kept together by vegetation, still persist. A 



Fig. S. Established dune at San Francisco. 



PHOTOGRAPH BY THE AUTHOB. 



series of small dunes follow and then we find the dunes assuming 

 greater and greater proportions. (Fig. 8.) The vegetation is scanty 

 and the sand drifts in all directions. The main advance goes, however, 

 eastward. Underh-ing these extensive sand deposits, is a kind of ar- 

 gillaceous sandstone, considered to be of Cretaceous age. 



All stages can here be observed, and the even sand surfaces on the 

 slopes of the great dunes offer good opportunities for observations of 

 the ripple phenomenon. 



The sand is coarse, mainly consisting of quartz, but is of a dark 

 color, and contains in some places an abundant admixture of organic 

 matter. After rain the surface is often almost gray. I found the 



