THE PHYSICAL PROPERTIES OF CLAY. 87 



will vary inversely with the diameter of the grains of the sand 

 from grains of 0.04 inch down to the finest sizes obtainable. 

 (2.) That the nonplastic ingredients of clay influence its tensile 

 strength inversely as the diameter of their grains, and fine- 

 grained clays will, other things being equal, possess the greatest 

 tensile strength." In other words, the coarser the grains of sand, 

 the less the tensile strength of the mixture containing them. 



In order to obtain some information regarding the relation of 

 texture to tensile strength the writer selected 5 clays at random 

 from the New Jersey series tested for this report, the only pre- 

 caution taken being to pick out samples ranging from high to 

 low tensile strength. These 5 samples were the following : 



1. Alloway clay from the railroad cut north of Alloway (Loc. 

 164, Lab. No. 680). This is a very plastic, slightly gritty, dense, 

 red-burning clay, with an average tensile strength of 453 pounds 

 per square inch. 



2. Pleistocene clay from the brickyard near Somerville (Loc. 

 234, Lab. No. 659). This was also a gritty, plastic clay, but not 

 as dense as the previous one. Its, average tensile strength was 

 297 pounds per square inch. 



3. A Cape May clay from along the river south of Millville 

 (Loc. 181, Lab. No. 645). A gritty, plastic clay, with an aver- 

 age tensile strength of 289 pounds per square inch. 



4. Sample of Raritan clay from Clifrwood (Loc. 220, Lab. 

 No. 615). A black, sandy, micaceous clay, with an average 

 tensile strength of 105 pounds per square inch. 



5. A soft, powdery, washed ball clay from near Sayreville 

 (Loc. 268, Lab. No. 723). It was plastic to the feel, with very 

 little grit, and a tensile strength of under 20 pounds per square 

 inch. 



Each of these clays was put through a mechanical analysis and 

 separated into the 5 classes of grains, 1 shown in the table below. 



The percentage of these sizes in each of the 5 samples is shown 

 in the following table : 



For explanation of sizes, see "Texture" in this chapter. 



