68 



plying the material for tile works and potteries. The clays lie 

 near the base of the formation close above the black shale of 

 the Devonian, and average about 40 feet in thickness, though 

 in places they reach 200 feet. The clay bed : s alternate with 

 seams of chert which are from 2 to 8 inches in thickness, while 

 the clay beds vary from 12 to 18 inches. The upper half of 

 the clay is more gritty than the lower half which often contains 

 material suitable for the manufacture of the finer grades of 

 porcelain ware. Analyses 5 to 8, in Table D, show the com- 

 position of several varieties of clay from this section. 



Lower Silurian and Cambrian. Associated with the cherty 

 limestones and brown iron-ore beds of the formations above 

 named beds of fine white clay, much of it china clay are not 

 uncommon. Analysis 9 of the table shows the composition of 

 a white clay from the brown ore bank at Rock Run, in Cherokee 

 County, where the clay is about 30 feet in thickness. Analyses 

 10 and ii are also from Rock Run. No. 12, from near Gads- 

 den, No. 13, from Blount County, and No. 14 from Oxanna, in 

 Calhoun County, are clays which seem to be adapted to cement 

 making. While no great number of the clays of these forma- 

 tions have been analyzed, they are known to be widely distrib- 

 uted 1 in Calhoun', Talladega, Jefferson, Tuscaloosa, and other 

 counties in connection with the browtn ore deposits. 



Cretaceous. In many respects the most important formation 

 of Alabama, in respect of its clays, is the lowermost division 

 of the Cretaceous, which has been called the Tuscaloosa, and 

 which is in part at least of the same geologic horizon as that of 

 the Raritan clays of New Jersey. The prevailing strata of this 

 formation are yellowish and grayish sands, but subordinated 

 to them are great lenses of massive clay varying in quality from 

 almost pure-white burning clay to dark-purple and mottled va- 

 rieties high in iron. 



The formation occupies a belt of country extending from 

 the north-western comer of the State, around the edges of the 

 Paleozoic formations to the Georgia line at Columbus. Its 

 greatest width is at the northwest boundary of the State where 

 it covers an area 30 or 40 miles wide in Alabama, and of about 

 the same width in Mississippi. The breadth at Wetumpka and 

 thence eastward to the Georgia line is only a few miles. The 

 most important part of this belt is where it is widest in Elmore, 



