58 IOWA ACADEMY OF SCIENCES. 



mentioned; or better still, east of a line drawn north and south through the city 

 of Ottumwa, number 109 of the map. With but a single exception, that at 

 Washington, number 54 of the map, these deeper borings furnish abundant 

 flows of water. But there are also, east of this north and south line, two smaller 

 areas of shallow wells whose characters are essentially identical with those 

 exhibited by the wells within the terminal moraine. One of these lies along the 

 Iowa river, see map, numbers 60-66, etc.; the other, and by far the smallest single 

 artesian area in the State, is in the valley of the Wapsipinnicon river, in Bremer 

 county, see map, numbers 11-12, 42. The shallow wells, therefore, constitute well 

 defined groups; the deep wells are widely scattered. 



It has been found convenient to classify the Iowa artesian wells in terms of the 

 geological structure which they exhibit. To the shallow v/ells, those that form 

 groups and which present similar geological sections, the term, '"glacial wells," 

 or wells of the first class, has been applied. To all others, no matter what may be 

 the geological age of the strata into which they may pass or in which they end, 

 the term " deep wells " or wells of the second class, may be appropriated. There 

 is no distinguishing mnemonic on the map by which these wells may be differ- 

 entiated. 



A few important deep borings have been made, in various parts of the State, 

 but more particularly in the northwestern and southwestern portions, in which 

 artesian waters were not found. But, in the greater number of these borings, the 

 waters rose to constant heights, always, however, some distance below the top of 

 the boring. These are called on the map '" deep wells not artesian" and are indi- 

 cated by a specific mnemonic, as in the well at Glenwood, in Southwestern Iowa, 

 see map number 120. 



In depth the glacial wells range from forty feet to two hundred and fifty feet 

 in a few cases; this feature is dependent on the relation of the borings to preglacial 

 drainage, on the one hand, and to the thickness of the morainic materials, which 

 is a variable, on the other. A generalized section may be given as follows, being 

 based upon the sequence of strata as exhibited in Hancock and Wright counties: 



Soil 1 to 5 feet 



Bouldery clay, with water 10 to 50 feet 



Sand and gravel 8 to 20 feet 



Bluish, bouldery glacial clays 30 to 120 feet 



Sand and gravel, with water 15 to 25 feet 



These materials are irregulary distributed over the surface of the State and 



exhibit a variable relation. However, whenever the gravels and sands of the 



lower series are reached, especially in the valleys of the larger streams within the 



terminal moraine, flowing wells are likely to be obtained. 

 The deeper artesian wells, or those which present the characteristic feature of 



penetrating the country rock are typified by the following section which is that of 



the deep artesian well at Cedar Rapids: 



No. Feet. 



1. Dark gray limestone 50 



2. Light gray limestone 85 



•8. Gray limestone 40 



*4. Coarse grained, reddish-brown limestone 65 



*5. Coarse, brown and very porous limestone 60 



♦Contains water. 



