116 



foley. SEDIMENTATION AND GROUND WATER 



TABLE 1 



Relation of Grain Size to Permeability 



[Ch. 6 



1 Includes clay. 



It is apparent from the table that, in general, the coarser grained 

 materials are more permeable than those with predominantly finer 

 grain. The table also shows that the proportion of large grains alone 

 is not necessarily significant, but that samples having a higher pro- 

 portion of small sizes generally have lower permeability. 



Wenzel (1942, pp. 21-50) lists a comprehensive bibliography on 

 permeability and laminar flow prepared by V. C. Fishel. 



The water-bearing properties of various rock types are not described 

 in detail in this chapter, and the reader is referred especially to 

 Meinzer (1923, pp. 117-148) for detailed descriptions. 



Special mention should be made of the limestones and associated 

 rocks as aquifers. Though normally they are compact fine-grained 

 rocks, they are excellent aquifers in many places where extensive open- 

 ings have been produced by fracturing and solution. The capacity of 

 the limestones and associated rocks to produce water is likely to be 

 erratic even within a small area, for if a well does not happen to en- 

 counter many or large fractures or solution channels it will have a 

 small capacity. Because of the continuous character of most of the 

 openings, the water from limestone formations is much more subject 

 to pollution than is the water that moves through the interstices be- 

 tween grains, as in sand and gravel. 



