1 88 CLAYS AND CLAY INDUSTRY. 



beds (Fig'. 36, B). The few instances known where borings have 

 shown that the fire clay is absent, although the overlying clays are 

 present (Fig. 36, C), are due probably to this interdepositional 

 erosion. 



The base of the clay is somewhat undulatory, but less so than 

 the top. Inasmuch as the basal undulations do> not correspond 

 with those of the top, the clay varies greatly in thickness. In- 

 stances of 40 feet have been reported, but the average is much less 

 than that. Most commonly there is but 6 to> 10 feet of the best clay, 

 and 20 feet is a fair average thickness, including the sandy top and 

 bottom. It is often much less than that. 



The fire-clay bed is found in the bottom of all the banks about 

 Woodbridge at present worked, except the Dixon banks (9, 10), 

 which go down to a lower level, and the Perth Amboy Terra 



f/(*36. //. Erosion along a valley through the drift laminated c lav 

 and f/re day. Bor/hys fr? bottom of the valley showdnly 

 fire sand. /ft/'/ le those on the raltey ■sides sir ike the c/ay 



B Partial erosion and removal of the f/re clay before the 

 over/y/ny laminated h/ack c/ays were deposited. 



C frosion a/vdremora/ of the f/re clay before the deposition 

 of the laminated clay which is here thicker than usual. 

 Borings here pass directly from the laminated c/ay into 

 the fire-sand. 



Cotta Company (7) which does not gO i deep enough. P. J. Ryan 

 ( 1 , 2, 8, 2 1 ) , William Berry ( 1 1 , 1 3 ) , M. D. Valentine & Bros. Co. 

 (14, 15, 23), J. H. Leisen (16), the Staten Island Clay Company 

 (17, 18, 19), Albert Martin (20), Anness & Potter (6), Henry 

 Maurer & Son (24), W. H. Cutter (29, 30), and J. P. Prall (31), 

 are the principal miners of this clay about Woodbridge, and the 

 various phases of the bed are shown in their banks. 



None of the banks near Spa Spring and Maurer Station now 

 go deep enough to reach the fire clay, its surface lying 10 feet or 

 more below sea level near Maurer Station. The same thing is true 

 of the banks between Florida Grove and Keasbey, wells along 

 the water-front between these places showing the fire clay to occur 

 far below sea level. 



