56 DOMESTIC WATER SUPPLIES FOR THE FARM 



The beds, being continuous, furnish water at practically every 

 point encountered, and since the head is usually known, the ob- 

 taining of flows is usually simply a question of elevation of the 

 surface and success or failure may be predicted in advance. 



Flows from Glacial Materials. Consisting largely of sands 

 and gravels, the glacial materials, next to the great sand and 

 sandstone beds, are naturally the most common source of flowing 

 wells. It is rare, however, to find individual beds extending for 

 any great distances, and the areas of flowing wells are, therefore, 

 usually of no great extent. What the areas lack in extent, how- 

 ever, is often largely made up in number, for in regions of thick 

 drift, like Michigan, there are literally hundreds of artesian 

 basins. In fact, throughout much of the Lower Peninsular, al- 

 most every valley or other depression of any magnitude yields 

 flows at depths commonly from 50 to 150 feet. Though not so 

 numerous in other parts of the country, local artesian basins 

 abound in the drift at many points. Unlike the case of the sand- 

 stones, in which the head of the water depends on the elevation 

 of distant outcrops, the head of the waters of the drift usually 

 depends on the altitude of closely adjacent elevations, often 

 within a mile or two of the artesian basin, and, since the differ- 

 ences of altitude are usually relatively slight, the pressures of 

 the drift waters are not usually high. 



Flows from Limestones. Limestones do not, as a rule, afford 

 many flowing wells. When near the surface, the water, because 

 of the solubility of the rock, generally finds easy escape, seldom 

 remaining confined under pressure. When below drainage level, 

 however, especially where the limestone lies between shales or 

 other impervious beds, artesian flows are not uncommon. The 

 flows in the vicinity of Cincinnati, on the Peninsula of Florida 

 and in portions of Texas are good examples of artesian waters of 

 this type. The volumes are often large. 



Flows from Granites. Granites, gneisses and other similar 

 crystalline rocks, although seldom regarded as a source of artesian 

 waters, nevertheless yield flowing wells at many points where the 



