222 GEOLOGY 



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drawing on the same reservoir, on the degree of imperviousness 

 of the confining bed above, etc. Flowing wells, often relatively 

 shallow, are frequently obtained from unconsolidated drift. 



Map work. Illustrations of the topographic effects of ground-water may 

 be found on a few topographic maps. Plates XC to XCIV of Professional 

 Paper 60, U. S. Geological Survey, are examples. Various reports on mining 

 regions, showing structure sections, afford illustrations of the economic 

 significance of one phase of work done by ground-water. 



