II. 



GEOLOGICAL RELATIONS OF THE 

 CLAYS OF ALABAMA, 



BY EUGENE A. SMITH, PH. D. 



The basis of all clays is kaolinite, the hydrated 

 silicate of alumina resulting from the chemical decom- 

 position of alumina bearing minerals which occur as 

 essential constituents of igneous rocks. In this de- 

 composition, as Dr. Kies has shown, the soluble con- 

 stituents are leached out while the kaolinite remains 

 behind as an insoluble residuum, more or less mixed 

 with the other nsoluble matters of the original 

 minerals. 



In this form the clay might be called a chemical 

 clay, since it is the direct result of a chemical decom- 

 position, having undergone no further modification 

 by being taken up, transported and redeposited. 



There is another form of residual clay which may 

 be distinguished from the above, and that is the clay 

 resulting from the decomposition of impure limesltone. 

 Naturally this variety is usually less free from foreign 

 matters than the otter. 



These residual clays taken up and redeposited by 

 running waters are incorporated in the stratified de- 

 posits of any later age. 



The clay deposits of the different geological form- 

 nations of Alabama have each its well marked pecu- 

 liarities, and the geological formations are clearly de- 



