CAMBRIAN AND SILURIAN FORMATIONS. 73 



conditions, the finer portions of these residual clays 

 may be taken in suspension 'in running waters and 

 redeposited at greater or less distances from their 

 place of origin in depressions, or along slopes. In 

 this way are oftem formed secondary deposits of 

 pretty fair plastic clays, sometimes mixed with sand 

 in proportion to serve well as material for good build- 

 ing brick. An illustration of this may be cited near 

 Wedowee in Randolph county, and there are many 

 instances where the residual clays of the country as 

 well as these redeposited masses are utilized both for 

 the manufacture of buildings brick of excellent 

 quality, and for pottery purposes. 



CAMBRIAN AND SILURIAN FORMATIONS. 



In these formations, the clay deposits are either 

 the residual clays left from the decomposition gen- 

 erally of the greait limestone formations of the Cam- 

 brian and Silurian, or concentrations of these resi- 

 dual clays by redeposition in sink holes, ponds, and 

 depressions; or the accumulation through sediment- 

 ary action ,in the depressions of these later forma- 

 tions, of (the chemical or vein clays of the Archaean. 



The two great limestones, above mentioned, are 

 rarely pure but are mixed with chert or other form 

 of siliceous matters, with iron, and with clay. Upon 

 their decay under the action of the atmospheric 

 agencies, these insoluble matters are left in the form 

 generally of reddish loam or clay capped with cherty 

 fragments, and i'mpregnatedi with iron. 



Such residual clays are extensively used in all our 

 valley regions for the manufacture of ordinary build- 

 ing brick, for which they are very well adaplted, the 



