CLAYS OF CAMDEN COUNTY. 395 



a large shallow excavation, with a working face 15 to 20 feet high, 

 involving- the following section : 



Section at Budd Brothers', Camden. 



Gravelly loam, 5 ft. 



Mottled green, yellow and pink, coarse-grained, sandy 



clay 6 ft. 



Dark, sandy, micaceous clay, 8 to io ft. 



The clay, the thickness of which is well shown in Plate XVIII, 

 Fig. 2, is mined by falling, and the run of the bank used. If too 

 much of the black clay is used the bricks are apt to burn grayish. 

 The top loam at times contains stones nearly an inch in diameter. 



A physical test was made in the laboratory of both the black 

 clay and the brick mixture. The chief difference between these 

 two would appear to be a slight decrease in the amount of water 

 required for tempering and in the fire shrinkage at cone oi. The 

 bricklet is also more porous, due to the presence of the loam, as 

 can be seen from the absorption. 



Physical tests of samples from Budd Brothers, Camden. 



Black clay and loam. Black clay alone. 



Lab. No. 620. Lab. No. 624. 



Water required, 20% 24% 



Air shrinkage, 6% 6% 



Average tensile strength, lbs. per sq. in., 156 164 



Cone 05 



Fire shrinkage 1.3 % 0.5 % 



Absorption, 16.54% 9-36% 



Color, red red 



Hardness, not steel-hard not steel-hard 



Cone 01 



Fire shrinkage, 1-5% 



Cone 1 



Fire shrinkage, 2.6 % 2. % 



Absorption, 12.68% 8.62% 



Color, red red 



Hardness, barely steel-hard barely steel-hard 



Cone 3 



Fire shrinkage, 2.6 % 2. % 



Absorption, 10.66% 10.75% 



Color, red red 



Hardness, steel-hard steel-hard 



Cone 5 



Fire shrinkage, 2.3% 



Absorption, 10.17% 



Color, red viscous at cone 8 



