56 SOILS. 



Of this character are the pine-forest soils of the coast region of the 

 Gulf of Mexico, particularly the " Sand hammocks " of the immediate 

 Gulf border, from Mississippi Sound to Charlotte Harbor, Florida ; the 

 sandy lands of the Grand Traverse region of Michigan, and many other 

 minor areas in the United States, usually characterized by a pine growth, 

 often more or less stunted, according to the nature of the sand grains. 



Calcareous sandstones usually form a very much better 

 class of soils, partly for the intrinsic reason given above as 

 regards limestones as soil-formers. The calcareous cement is 

 very rarely pure calcite; in most cases it is very impure, as, 

 most commonly, is also the " sand " itself. This is explained 

 from the fact that such rocks (mostly soft and often quite un- 

 consolidated) are, like limestones themselves, the result of de- 

 position in shallow seas or lakes, receiving deposits from the 

 land drainage, and enriched by the animal and vegetable life 

 of such waters. Not uncommonly they contain, disseminated 

 through them, grains of the mineral glauconite (a hydrous 

 silicate of iron and potash), which readily supplies available 

 potash ; while the remnants of animals and plants furnish 

 more or less of available phosphates. Thus the general pre- 

 sumption regarding calcareous sandstones is that the derived 

 soils are of good quality, frequently of the very best. The 

 same, however, does not appear to be true of sandstones cem- 

 ented by dolomite; the soils derived from magnesian sand- 

 stones are in many cases noted for their unproductiveness. 

 (See chapt. 3, p. 42). 



Ferruginous Sandstones manifestly derive no important soil 

 ingredients from their cement when the latter is measurably 

 pure ferric hydrate; and when in addition the sand itself is 

 purely siliceous, the soils resulting from the disintegration of 

 the rocks are very poor. 



Such are, e.g., the soils derived from the ferruginous sandstones of the 

 Lafayette formation in a part of northern Mississippi and adjacent por- 

 tions of Tennessee and Alabama, characterized by small srrubby oak or 

 dwarfed pine. On the whole, however, such purely ferruginous quartz 

 sandstones are exceptional, and should not detract from the favorable 

 inferences usually to be drawn from the iron-rust tint of soils (see 

 chapter. 15 



