CLAY-BEARING FORMATIONS. 353 



viz, those from localities 161 and 165, are nearly impervious at 

 the above-mentioned cone. Few of them become viscous below 

 cone 12 while some do not fuse until cone 27 is reached. 



Uses. — The Alloway clay at the present time is worked at one 

 locality for making brick and draintile, and yields excellent re- 

 sults, the bricks showing up well on both cross-breaking and 

 crushing test. Indeed, it would seem that these clays were worth 

 being tried, also, for the manufacture of stoneware, not alone, 

 perhaps, but mixed with other materials. 



Talc-like, micaceous sand. — This material, which is found un- 

 der the Alloway clay, in the vicinity of Woodstown (p. 144), is 

 a highly micaceous clayey sand, of a whitish color when un- 

 weathered. It has very little plasticity, and absorbs considerable 

 water, viz., 38.5 per cent, in one case and 45.2 per cent, in another. 

 The air shrinkages were 3.3 per cent, and 5 per cent., but the 

 material does not get steel-hard until cone 5 to 8, and the burned 

 bricklet is exceedingly porous, for one at cone 10 had an ab- 

 sorption of 19.23 per cent. 



It is doubtful if this material has any value, if used alone, but 

 as a packing material or filler it could no doubt find application. 



ASBURY CLAYS. 



The character of these clays is in marked contrast to those 

 found about Alloway, which are higher in the Miocene, and their 

 distribution is rather restricted. They form a series of beds or 

 lenses of thinly-laminated character, the layers of clay being 

 separated by thin layers of sand. The clays are thus nearly 

 always gritty, some containing so much sand that even at cone 

 9 they do not burn dense. The excess of sand has also the ad- 

 ditional effect of decreasing the plasticity, tensile strength, air 

 and fire shrinkage. The clays show many coarse grains of quartz 

 and numerous scales of mica. In some beds the sand layers are 

 cemented by iron and these lumps of limonite sand are very 

 likely to cause splitting of the bricks, or fused spots in burning, 

 unless they are separated by screening or broken up in tempering. 

 Furthermore, in any one locality, the section shows beds of dif- 

 23 cl G 



