CLAYS OF BERGEN COUNTY. 373 



BERGEN COUNTY. 



Hackcnsack and Little Ferry. — The extensive deposits of brick 

 clay which occur between Hackensack and Little Ferry, and also 

 south of the latter point, have already been described somewhat in 

 detail, pp. 124-128. They are quite uniform in character, so> that 

 the following test of a sample will serve to indicate their physical 

 properties. Water required for mixing", 22 per cent. ; air shrink- 

 age, 6 per cent. ; average tensile strength, 108 pounds per square 

 inch. 



At cone 05, fire shrinkage 4.3 per cent., absorption 7.88 per 

 cent., color good red, bricklet nearly steel-hard. 



At cone 01, fire shrinkage 7.3 per cent., absorption .28 per cent., 

 bricklet red. At cone 1 bricklet practically vitrified, fire shrink- 

 age 8.6 per cent., absorption .1 per cent., color good red. 



At cone 3 the clay was beyond vitrification, and it had begun 

 to swell so 1 that its fire shrinkage was only 7 per cent. ; in fact, it 

 was unable to hold its shape at this point. In actual practice the 

 clay is always mixed with a, certain proportion of the overlying 

 sand, in order to reduce the fire shrinkage and make it stand up 

 better in burning. The bricks are always molded by the soft-mud 

 process and burned in scove kilns. 



Analyses of common-brick clays. 



Little Ferry. Hackensack. 



Silica ( S1O2) , 66.67 S969 



Alumina (A1 2 3 ), ' 18.27 ) 



Iron oxide (F^Os) , 3.1 1 ) 2 4-°5 



Titanic oxide (Ti0 2 ), 0.85 0.44 



Lime (CaO), 1.18 1.63 



Magnesia (MgO), 1.09 2.03 



Potash ( K 2 ) , 2.92 0.54 



Soda (Na 2 0), 1.30 2.39 



Water (H 2 0), 4.03 4.85 



Moisture, 0.80 



Total, 99.42 96.42 



Total fluxes, 9.60 



