128 Artesian Well Boring in Southeastern Minnesota — Hall. 



II. 



Almost the first thing which a community demands is a sup- 

 ply of wholesome and abundant water. This demand is often a 

 factor which locates centers of population and commercial in- 

 terests. To bring from a distant and uncontaminated supply 

 enough water for human needs, always requires the expenditure 

 of large sums of money, as population increases and local supplies 

 have become contaminated. 



In our western states, with their level surface over large 

 areas, and the consequent scarcity of springs, the question of a 

 sufficient water supply becomes a very serious one in every com- 

 munity. Along our streams the excessive cost of a large supply 

 is put off by the pumping station or the conduit from a higher 

 level. The objections against such a supply have led some com- 

 munities and several private individuals to attempt to secure, by 

 boring artesian or deep wells, a supply free from those objectionable 

 (jualities which our river water is universally admitted to possess. 

 A number of artesian wells in the upper Mississippi valley is the 

 successful result of their efforts, and as this mode of securing a 

 supply of water will be more and more followed, it is proposed in 

 this paper to give a hurried outline of the geology of the Missis- 

 sippi river valley so far as that valley lies in Minnesota, and tell 

 what experience has pointed us toward, rather than what it has 

 proved to us in the matter of deep wells in the southeastern por- 

 tion of the state. 



Around the headwaters of the Mississippi and around all its 

 tributaries southward from Lake Itasca to a point this (south) 

 side of Saint Cloud, the underlying rock is Archean. In part it 

 consists of schists and slates, usually regarded asHuronian, and in 

 part of gneisses of Laurentian time with eruptive granites and 

 diabases. From the northeast to the southwest these rocks stretch 

 entirely across the state. In all these areas experience gives no hope 

 whatever that water will be found by boring into these rocks. 

 They are covered however, by a layer of glacial drift, which reaches 

 in places a thickness of 250 feet. This drift covering can contain 

 vast quantities of water from that supply percolating into it from 

 the yearly rains and snows. In this drift, then, must lie the chief 

 supply of spring and well water for the whole region. 



But to the south and east of the area named, younger rocks 

 occur. They are of Cambrian and Silurian age. Their limit in 



