190 CLAYS AND CLAY INDUSTRY. 



position and elevation, as well as its general appearance, indicate 

 that it belongs to this horizon. 



Intermediate beds. — Although the black laminated clays and 

 sands at the top and the fire clay at the bottom are the only two 

 subdivisions of the Wooclbridge clays which can be generally rec- 

 ognized, yet between them there are a few beds which locally be- 

 come somewhat conspicuous. 



The fire clay is often, but not always, overlain by a bed of dark 

 sand or sandy clay, which is usually rejected by the miners. This 

 bed was somewhat fully described by Cook and Smock in the Clay 

 Report of 1878, 1 from which the following sentences are quoted: 



"Lignite or, as it is more commonly termed, wood, and pyrite 

 (sometimes known as 'sulphur balls') are also common in this bed, 

 and the dark color of the sandy mass is often due to the amount 

 of carbonaceous material disseminated in small fragments and 

 particles through it. This is sometimes so abundant that the bed 

 appears made up oi many thin layers of compressed woody mat- 

 ter in the form of flattened limbs and trunks of trees and leaf im- 

 pressions packed so closely together that it is difficult to get good 

 specimens or well marked prints. These all lie with the stratifica- 

 tion, that is, with their longer axes conformable to the plane of 

 bedding. In the banks of H. Cutter & Sons [now W. H. Cutter], 

 and at Sayreville, the bed seems like a great herbarium, with its 

 specimens nicely pressed and preserved in the sandy layers." 



The leaf-bed has been recognized at seven or eight different 

 banks, but our studies have failed to convince us that the bed is 

 well enough characterized or persistent enough to be recognized 

 over the whole district. 



In a number of banks north of Keasbey, a white or light- 

 colored, sandy clay occurs a little way above the fire clay and 

 stands in somewhat marked contrast to the lignitic clays or sands 

 between it and the fire clay. It varies in thickness from 2 to 10 

 feet, with an average of 3 or 4. This clay has been called the 

 "top-white" clay, and is used for retorts, stoneware, etc. In other 

 banks a well-marked black or dark-blue plastic clay of generally 

 greater thickness than the top-white occurs at about the same 



1 pp- 53-54- 



