THE CLAY-MINING INDUSTRY. 339 



TRENTON AREA. 



Sagger, wad and fire clays of Raritan age are dug in a number 

 of pits at Dogtown, east of Trenton. Most of the product is 

 hauled by wagon to Trenton for use in the potteries there. The 

 number of firms or individuals actively and permanently in opera- 

 tion does not exceed three, but the clay is sporadically dug by 

 others. Detailed tests of the Dogtown clays are given under 

 Mercer county, Chapter XIX. 



DELAWARE RIVER AREA. 



Semirefractory fire clays are dug in several pits near Palmyra. 

 These are shipped chiefly to Philadelphia and other nearby towns 

 for terra cotta and foundry use. The deposits are overlain by a 

 great thickness of sand, which is the chief product of the pits, the 

 clay being excavated in but comparatively small quantities from 

 the bottom. 



WOODMANSIE AREA. 



This represents a small area of Cohansey clay mined near Old 

 Half Way, in Ocean county, and shipped mostly to Philadelphia 

 for terra-cotta manufacture. 



METHODS OE MINING. 



The methods used for mining the clay by square pits, as prac- 

 ticed in the Middlesex and Trenton districts, have already been 

 referred to in Chapter II. It may appear to some that this system 

 of mining, as extensively practiced in the Woodbridge district, 

 is not the best that can be adopted, and yet, under the conditions, 

 it is probably the most practicable, since the frequent change in 

 character of the beds both vertically and laterally prohibits any 

 methods involving the digging of the clay on a larger scale. This 



