BEACH SANDS 829 



What is described by Whitney^ as a typical swamp, bog or 

 peat soil, from a rice field near Georgetown, South Carolina, 

 yielded the results given on the preceding page, columns III and 

 IV being simply recalculated from I and II on an organic and 

 water-free basis. These are the so-called sob-field soils, in them- 

 selves poor, but responding readily to fertilizers. When ex- 

 hausted by cultivation, they recuperate quickly through the aid 

 of silt deposits from the rivers, brought about by the continual 

 ebb and flow of the tides. 



Beach Sands, — Although differing radically in composition 

 from the sea-coast swamp deposits already described, one must, 

 on account of their intimate geological relationship, include here 

 a bx'ief description of those fragmental deposits formed by wave 

 action along beaches and in many instances almost absolutely 

 free from organic matter of any kind. Such are the clean 

 white beach sands, the delight of the summer visitor at the sea- 

 sides. These are found here and there in isolated stretches 

 along the Atlantic slopes, particularly where, as at Old Orchard, 

 Maine, they receive the full sweep of wave and tide from the 

 open sea. In many instances the material forming these beaches 

 is siliceous sand from glacial deposits which the ocean has 

 reassorted according to its own liking. In other cases it is 

 sand brought down by rivers, which has undergone fractional 

 separation through the varying strength of transporting agencies. 

 In still others it is material derived immediately from the shore 

 rocks through the weathering action of atmospheres and the 

 hammering of the waves. In other cases yet, as along the coasts 

 of Florida, the source is problematical. It can only be said, 

 knowing the character of rocks forming the mainland, that they 

 could not have here originated, but must have been transported, 

 and probably down the coast, from the areas of crystalline rocks 

 to the northward. It is sometimes, though not always, possible 

 to gain an idea of the probable source of these sands, through a 

 study of their mineralogical nature and the physical condition 

 of the individual particles. 



Sorby, who devoted careful attention to the microscopic ap- 

 pearance of granules of quartz sand belonging to various geo- 

 logical periods, divided them into five types, ** which though 



iRice, Its Cultivation, Production, and Distribution, Eep. ISTo. 6, Misc. 

 Series, IJ. S. Dept. of Agriculture, 1893. 



