496 CLAYS AND CLAY INDUSTRY. 



Burning tests of brick mixture. D. F. Haines, Yorktown. 



Fire shrinkage. Color. Hardness. Absorption. 



Cone 05, 1% red not steel-hard 1342% 



Cone 01, 2.7% red nearly steel-hard 8.58% 



Cone 1, 2.7% red steel-hard 8.9% 



Cone 3, 4.4% red 6.96% 



Cone 8 5.7% red 1.21% 



It will be seen that the two clays alone do> not differ much in 

 their air shrinkage, but that the bottom, clay has a much higher 

 fire shrinkage, and at cone 05 is nearly twice as dense as the top 

 clay. 



The mixture has had its air shrinkage as well as its fire shrink- 

 age decreased by the addition of loam. Its composition was as 

 follows : 



Chemical analysis of brick mixture. D. F. Haines, Yorktown. 



Silica (SiO,), 68.96 



Alumina ( AI2O3) , 17.87 



Ferric oxide (Fe 2 3 ) , 3.27 



Lime (CaO), 0.25 



Magnesia (MgO), 0.25 



Alkalies (Na 2 0, K2O), 2.10 



Water (H.O), 6.95 



Total, : 99-65 



Total fluxes, 5.87 



The Alloway clay also outcrops at a point west of Yorktown 

 in the ditch along the north side of the road (Loc. 161). The 

 clay, which is a yellow-mottled color, is at least 4 feet thick, as 

 determined by boring (total thickness probably much greater) T 

 and is covered by 6 to 7 feet of Bridgeton gravel. The latter thins 

 out, however, down the slope to the west, as well as on the south 

 side of the road. The clay (Lab. No. 691) is quite plastic to the 

 feel, has little grit, but mica scales are fairly abundant in it. It 

 took 36.1 per cent, water to mix it, and its air shrinkage was 8 

 per cent. A bricklet burned at cone 1 had a fire shrinkage of 7 

 per cent., which is somewhat high. Its color was brownish red, 

 and its absorption only 1.41 per cent., showing its dense-burning 

 character. 



