THE PHYSICAL PROPERTIES OF CLAY. 115 



with a film of paraffin. The former method, therefore, considers 

 the specific gravity of the clay to be the same as its mineral 

 grains, while the latter method considers the pore spaces between 

 the grains as a part of the clay mass, and the specific gravity 

 depends consequently both on the porosity and mineralogical 

 composition. 



