636 W. H. SHERZER RECOGNITION OE TYPES OF SAND GRAINS Ij 



County, from which the beach sands of this portion of the gulf were 

 probably derived, he writes : 



"The considerable depth of sand forming the top part of the section alonj 

 the bluffs facing Pensacola Bay, these sands are of the type that I regard as 

 residual. The upper several feet are bleached white. Such iron staining as 

 they may have possessed originally is likewise carried away through the leach- 

 ing effect of rain water. Our summer rainfall is extremely heavj^ and the 

 minute clay particles which originally formed part of the formation have been 

 carried away by mechanical wash. Beneath these light colored superficial 

 sands is found the sand in less complete condition of decay, at this depth being 

 mottled, iron-stained, and containing more or less fine clay mixed with the 

 sand. ... It appears to be a formation originally deposited in compara- 

 tively shallow water with conflicting currents, resulting in irregularities in 

 deposition and in cross-bedding. The materials doubtless came from the con- 

 tinent to the north. . . . The nearest igneous rocks which must have been 

 their original source lie some 500 miles to the northwest." 



According to this interpretation, the Escambia beach sand is being the 

 second time worked on by the waves, the residual agencies just preced- 

 ing presumably having had little effect upon the granules themselves. It 

 appears to represent the extreme type of aqueous sand. Merrill has 

 briefly described and figured what appears to be an identical sand from 

 the beach of the neighboring Santa Eosa Island.^® At West Palm Beach, 

 on the Atlantic side of the state, there occurs the same type of sand, 

 which has been presumably transported many miles along shore from the 

 Piedmont region to the north, yielding the subangular type of granule 

 and eliminating practically everything but quartz. ^^ 



In glaciated and adjacent regions the bulk of the sand handled by 

 streams and the waves of the lakes and seas is very probably of glacial 

 origin, while in non-glaciated areas it is either largely residual or derived 

 from the parent beds directly by the erosive action of the water itself. 

 For volcanic sands rehandled by the water the compound term aqueo- 

 volcanic is expressive, but is not intended to be applied to a sand result- 

 ing from the direct action of water on an ordinary lava bed. It is scarcely 

 to be expected that volcanic sands of the rounded type can be distin- 

 guished from aqueo-volcanic sands except by evidence based on the nature 

 of the depositing agent. About the shores of volcanic islands aqueo- 

 volcanic sands must occur not infrequently, and in cases such as clearing 

 their valleys of the vast quantities of ash derived from La Soufriere, in 

 1902, the Wallibu and Eabaka rivers, on the Island of Saint Vincent, 



19 Rocks, rock-weathering, and soils, p. 343. 



20 See Shaler's paper, "Ptienomena of beach and dune-sands." Bulletin of the Geo- 

 logical Society of America, vol. 5, 1894, p. 208. 



