CLAYS AND CLAY INDUSTRY. 



Mechanical Analyses of some New Jersey Clays. 



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Conventional Lab. Lab. Lab. Lab. Lab. 



Names. No. 680. No. 659. No. 645. No. 615. No. 723. 



Clay substance, 59.00% 44.00% 22.00% 30.645% 87.96% 



Fine silt, 11.00 7. 11 5.66 14.21 6.95 



Silt and fine sand,... 14.70 24.35 26.55 5-585 3.00 



Medium sand, 3.50 7.80 H-45 6.400 1.00 



Sand, 11.40 16.35 33-44 42-95° 



99.60 99.61 99-io 99-790 98.91 



These figures seem to throw some light on the relation of the 

 texture to the tensile strength, but, while highly suggestive, are 

 not to be taken as final. The writer hopes, however, to- have the 

 opportunity of supplementing them by additional tests at some 

 later date. Before discussing the bearing of the mechanical 

 analyses given above it seems desirable to- plot them in the form 

 of curves, as shown in Fig. 27. Here the horizontal lines rep- 

 resent percentages. Of the 6 columns, the first 5 represent the 

 grain sizes and the sixth the tensile strength. 



Taking No. 5 of the above table of analyses we find that it 

 contains 87.96 per cent, of clay substance. This point is plotted 

 in the first column. The point representing the percentage of 

 fine silt is then plotted in the next column, and so on with the 

 other sizes. These points are then connected with a curved line. 

 In the same way the percentages of the different sizes of grains 

 of the other samples were plotted and connected by curved lines. 

 The lines are drawn in different ways so that those representing 

 the different clays can be more readily distinguished at a glance. 

 From a study of this table it is seen that the clay having the 

 lowest tensile strength (No. 5) contains a very high percentage 

 of the finest clay particles. Furthermore, the clay having the 

 second lowest tensile strength (No. 4) contains the largest per- 

 centage of sand (42.9 per cent.). From this it appears that an 

 excess of either coarse or fine grains lowers the tensile strength. 

 On the other hand, in those clays having the high tensile 

 strength the percentages of fine, medium and coarse particles are 



