CLAYS OF CRETACEOUS FORMATION. 197 



itan potter's clay resting on red shale has been worked in times 

 past at several points, and at present is dug by the Excelsior Terra 

 Cotta Company for use in their works at Rocky Hill. An anal- 

 ysis of this clay is given in Chapter XIX, under clays of Somerset 

 county. 



Overlying the clay bed, which is said to reach a thickness of 14 

 feet in places, is a quartz sand, which is undoubtedly to be cor- 

 related with the fire-sand bed near Woodbridge. 



TRENTON CIvAYS. 



Two miles east of Trenton clays are dug in a number of pits 

 along Pond run. These are locally known as Dogtown clays. 

 The stripping, chiefly Pensauken gravel, varies from 5 to- 12 feet 

 in thickness. The clay is commonly red or red-spotted, grading 

 into a blue at the bottom of the pits. In some places the upper 

 layer is a white clay, and locally a black lignitic clay occurs be- 

 neath the blue clay. Elsewhere a sand bed underlies the clay. 

 The most extensive diggings are those of James Moon (101) 

 (Plate VI). The general section as reported by Mr. Moon is as 

 follows : 



Section at pits of J. J. Moon, Dogtown, near Trenton. 



Stripping, chiefly gravel, 5-12 ft. 



White clay (where stripping is thin) , 2-3 ft. 



Red clay, grading down into a red-spotted and thence 



to a blue clay, 14-28 ft. 



Sand, 3-4 ft. 



Hard, tough, blue clay, called "hard-pan," 3-4 ft. 



Loose, white sand, more than 8 ft. 



Somewhat similar clays are dug on the J. Priest farm (100), 

 by D. South (102), by A. Lattimer (105), by J. Kuhn adjoining 

 Lattimer's pits, and on the A. Worthington property (104). 

 Priest's clay is reported to- range from 16 to 22 feet in thickness, 

 Moore's 18 to 32, South's 10 to 14 feet, and Lattimer's 15 to 22 

 feet. They are used chiefly for saggers and wad, and are hauled 

 by wagon to the Trenton potteries. Clay has also been found at 

 other points in this neighborhood, but the pits are no longer 



