CLAY-BEARING FORMATIONS. 347 



bank, and the one showing the highest water absorption did 

 not show the highest air shrinkage. 



Tensile strength. — The tensile strength was determined in 10 

 samples of this group, and was high in the majority. It ranged 

 from 90 pounds per square inch to 291 pounds per square inch. 



Burning. — As will be seen by reference to the table, p. 348, the 

 different clays of this group show a great variation in their fire 

 shrinkages. Thus, for example, at cone 1 we find fire shrinkages 

 ranging from 1 per cent, up to 7.6 per cent., while the absorption 

 varies from 14.49 per cent, to 3.08 per cent. The greater number 

 of the samples tested burned red and moderately hard at cone 1. 

 Those from Buckshutem (Loc. 180) and south of Millville (Loc. 

 181) became steel-hard at cone 03. The mixture of Fish House 

 clays was the most dense burning of the series, even though its 

 fire shrinkage was not high. 



In some deposits, clays of quite dissimilar character are obtain- 

 able, as for example at Woodbine (Loc. 189), where both a red- 

 burning and buff-burning clay are found in the same bed. The 

 former gives a good hard brick at cone 1, but the latter does not 

 become steel-hard until above cone 3, burning to a light-buff 

 product at cone 5, and to a buff of slightly grayish shade at cone 

 8. There is not much difference in the fire shrinkage of the two. 

 The difference in color of the two> clays after burning is seen in 

 the bricks made of these clays, the more refractory clay showing 

 as whitish spots. 



At cone 5, several samples, viz., those from localities 190, 181 

 and 188, gave good hard bricklets, two of which had a low ab- 

 sorption. 



The one showing the highest heat-resisting power, viz., sample 

 No. 678 from locality 189 (Woodbine), may be a clay of low 

 refractoriness, as at cone 15 it was not vitrified. Two samples 

 were burned to cone 10 and one to 1 cone 12. Of the former, one 

 (Loc. 190) softened sufficiently to< lose its shape. The one heated 

 to> cone 12 (Loc. 178) burned gray buff, and was nearly vitrified 

 but showed no warping or twisting. 



Uses. — The clays of this group are worked chiefly around 

 Trenton for making common and some pressed brick. East and 



