THE PHYSICAL PROPERTIES OF CLAY. 113 



greatly in different clays. Open, porous, sandy ones fall rapidly 

 to a powdery mass ; others may spall or chip off slowly when 

 immersed, while still others either do not slake at all, or only 

 after long soaking. The slaking property is one of some practical 

 importance, as easily slaking - clays temper more readily, or, if 



Fig. 34. 



Particles of a Clay Marl I, enlarged 362 diameters. 



the material is to be washed, it disintegrates more rapidly in 

 the log washer. 



The slaking qualities of the clays from the different formations 

 are referred to in Chapter XVIII, where the different groups are 

 discussed collectively. 



cl G 



