142 CLAYS AND CLAY INDUSTRY. 



be older than late Miocene, and, as above noted, they may be 

 younger. It likewise enables us to fix the age of the thick bed 

 of clay which occurs beneath it, so that, although it contains no 

 clay itself, it is an important stratigraphical bed. 



THE ALLOWAY CLAY. 



Occurrence.- — The clay bed, to which we have given this name, 

 is continuously traceable from near Swans Mills, south of Mullica 

 Hill, in Gloucester county, southwest to a point 2 miles south of 

 Alloway, in Salem county. Isolated outcrops, where the over- 

 lying beds have been removed, have been observed as far south 

 as Stow Creek township, in Cumberland county. The clay un- 

 doubtedly continues south of Quinton, towards Canton, and per- 

 haps southeast to Bacons Neck, near Cohansey creek, but in this 

 direction it is deeply buried beneath the later Cape May sand and 

 gravel. Within the area between Alloway and Ewans Mills, its 

 outcrop forms an exceedingly irregular belt, several miles in 

 width. Within this belt, however, there are considerable areas 

 where the overlying Bridgeton formation is SO' thick as to effect- 

 ually conceal the clay which lies beneath. The map on Plate 

 XIII (in pocket) shows the areas (1) in which this clay appears 

 on the surface or is buried by not more than 5 or 6 feet of cover; 

 (2) the areas in which it is so deeply buried as to be inaccessible, 

 and (3) the areas from which it has been removed by erosion. 

 Since the clay bed slopes gently towards the southeast, the north- 

 western border of this deposit is formed by the outcrop of under- 

 lying beds from which the clay has been eroded. Attempts to 

 find this clay to the northwest of the area indicated on the map 

 by boring or otherwise will, therefore, prove futile. On the 

 southeast and south, however, the Alloway clay passes beneath 

 younger formations of various ages. These rapidly attain con- 

 siderable thickness, particularly to the southeast, owing to the 

 rise of ground in that direction, so that, although the clay there 

 continues an unknown distance to the south and southeast be- 

 yond the limits given on the map, yet it is discoverable only by 



