IMPORTANCE OF OPENINGS IN SANDSTONES. 



133 



of meters. This is well illustrated by the strata bearing artesian water, 

 many of which certainly transmit great quantities of water for hundreds of 

 kilometers. An excellent illustration of porous strata of this class is the 

 Dakota sandstone. This sandstone yields great quantities of water alono- 

 the James River Valley, and the nearest feeding area, so far as known, is 

 in the Black Hills, 400 kilometers distant. The volume of water which issues 



Fig. 4. — Spheres packed in the most compact manner possible, sh< 

 ings in one direction. After Slichter. 



continuous open- 



from sandstone strata in artesian basins shows how important is the class of 

 openings under consideration. 



Since the continuous openings of sediments are commonlv limited to 

 a formation, it is plain that such openings are very faA T orable to the flowage 

 of water along a formation, but are less potent in the transference of water 

 from one stratum or formation to another. 



(3) Irreg'ular openings are those of the vesicular lavas and of the 



