METHODS OF WORKING CLAY DEPOSITS. 35 



or other layers that are sometimes interstratified with the clay. 

 The surface drainage is commonly diverted by means of ditches 

 dug around the top of the pit (Plate VIII, Fig. 2). In some 

 districts there is a bed of water-bearing sand underlying the 

 lowest clay dug, and, as this is approached, hand pumps have 

 to be used to- keep down the water until the last spit of clay is 

 all taken out. 



In digging a pit of clay, it is well to avoid discarding a clay 

 of lower grade, or mixing it with the dirt stripping, because 

 it has no< market value at the time. Careless handling of the 

 medium-grade clays in the Woodbridge and Perth Amboy dis- 

 tricts in the early days of their activity has been the means of 

 spoiling much clay that would now be salable. 



At most other localities in the State the clay is obtained from 

 banks or large irregular pits (PI. VII, Figs. 1 and 2), and the 

 run of the bank or pit is commonly used, although the clay 

 worker may find it preferable to dig at some particular point, or 

 points, because of local improvements in the clay. No attempt 

 is then made to- hold up the other parts of the bank, as the 

 excavation is so large that a small amount of washing does not 

 affect the work in other parts. Since surface waters often trickle 

 through the soil until they reach a clay surface and follow it, 

 there is not infrequently a series of small springs emerging 

 along the top of a clay bank, and the water from these is usually 

 diverted by means of properly constructed ditches. In addition 

 to these ditches, however, it is commonly necessary to have- 

 additional ditches on the ground at the base of the bank. If 

 the bank is high, that is seventy-five feet or more, it is safer 

 to work it in several benches or steps, and not as a vertical face,, 

 for this will be apt to slide. Neither should the factory be 

 located close to the base of such a bank, for there is danger of 

 slides in case the clay becomes soaked, and the writer has seen 

 several instances in which yards have been buried in this manner. 



When clay deposits are worked as a bank or large pit, the 

 clay is commonly dug by means of pick and shovels, but, if the 

 scale of operations warrants, a steam shovel (PI. VIII, Fig. 1) 

 is far better and more economical. The latter method is used at 

 Lorillard, Keasbey, Sayreville and South River. If the clay is 



