114 



CLAYS AND CLAY INDUSTRY. 



SPECIFIC GRAVITY. 



The specific gravity of a clay stands in more or less close 

 relation to the density of its mineral particles, and affects its 

 weight per cubic foot, but most clays do not vary much in their 

 specific gravity, ranging commonly from about 1.80 to 2.60. 

 That is they weigh 1.80 to 2.60 times as much as an equal 

 amount of water. 



The specific gravity of a number of samples from New Jersey 

 was determined and the figures are given below. It will be 

 noticed that there is not as much variation as one might expect. 



Specific Gravity of New Jersey Clays. 



■Pleistocene and post-Pleistocene. 

 Locality 



No. 

 291, 



234. 

 127, 

 276, 

 290, 

 181, 



Lab. No. 



. 618 



• 659 



• 651 

 . 726 



■ 727 



■ 645 



Sp.G. 

 2.68 

 2.68 

 2.64 

 2.60 

 2.60 

 2.63 



Locality 

 No. 

 167, . . 

 164, . . 

 162, . . 

 169, . . 

 160, . . 

 162, . . 



Alloway. 



Lab. No. 



680 

 617 

 674 

 675 

 677 



Sp.G. 



2.49 

 2.52 

 2.55 

 2-59 

 2.44 



2-54 



Cohansey. 



Asbury. 



183, 

 185, 

 185, 

 206, 

 209, 

 182, 

 195, 

 195, 

 191, 

 183. 

 218, 



653 

 683 

 682 

 66s 

 666 

 661 

 642 



634 

 619 

 663 



69S 



2-53 

 2.61 

 2.58 

 2.84 

 2.62 

 2-55 

 2.64 

 2.64 

 2.63 

 2.60 

 2.62 



217, 



222, 

 222, 

 220, 

 109, 

 268, 

 120, 

 134, 



697 



Raritan. 



2.47 



603 



2.69 



606 



2.6a 



615 



2.39 



600 



2.59 



723 



•2.34 



654 



2.60 



621 



2.65 



If we compare these figures with the figures obtained by Prof. 

 Cook in 1878, we find that his were in most cases much lower, but 

 the reason for this is due to the fact that the determinations 

 for this report were made on the clay powder with a pycnometer, 

 while those in the 1878 report were on lumps of the clay coated 



