132 Artesian Well Boring in Southeastern Minnesota — Hall. 



under the Devonian in Mower and to the westward. The thick- 

 ness of this formation at Minneapolis is 164 feet, and in the south- 

 ern counties, in those locations where it can be measured, it has 

 been found by N. H. Winchellto be as thin as 115 feet.* It may 

 he said in passing, that Professor Chamberlin has found this 

 ■same formation in Wisconsin, where it is widely distributed, 

 varying in thickness "from two hundred and twelve feet down to 

 a single layer of sand grains.'^f 



The porous condition of this sandstone enables large quanti- 

 ties of water to percolate through it and saturate it, but its high 

 position in this state prevents a flow from it. Yet by means of 

 pumps and stationary engines large quantities of water may be 

 drawn. 



C. The Shakopee A.— All geologists of the northwest are not 

 agreed to refer the St. Peter sandstone to the Silurian; indeed, the 

 burden of opinion inclines to the Cambrian age as its true refer- 

 eiiee. But immediately below it is the Shakopee, a great forma- 

 ition which is undoubtedly Cambrian. This was first noted as a 

 'distinct bed of dolomite and dolomitic limestone at Shakopee in 

 1873.J "Its thickness in Minnesota varies from 96 feet at 

 Shakopee to 200 feet in Houston county; in southeastern central 

 Wisconsin it is from 50 to 250 feet; in eastern Wisconsin 62 to 141 

 feet; in Missouri, as the Second Magnesian limestone of Swallow, 

 it is 230 feet in thickness. In the Minnesota reports this is the 

 limestone of the Minnesota valley, and both the Shakopee and St. 

 Lawrence in the southeastern counties, e. g. Houston, Winona, 

 Olmsted and Fillmore, except the limestone referred to the 

 St. Lawrence at Whalen and Lanesboro. It is the Shakopee 

 of well borings at Minneapolis, Mendota, St. Paul and Hastings." 



7. Elevator B Saj^dston^e. — "This formation (the Shako- 

 pee) encloses a more or less persistent layer of sandstone 20 feet in 

 thickness in the well at Elevator B, St. Paul, which is probably 

 the Jordan sandstone of Houston and Fillmore counties, 

 except perhaps Lanesboro; of Olmsted county, except perhaps 

 <^uincy. 



^^ The sandstone found in this formation at Elevator B may 

 Ije the cause of the terrace made bv the lower part of this 



*Geologieal and Natural History Survey of Minnesota. Final report, 

 Vol. I, p. 650, and at other places in the county descriptions, 

 topology of Wisconsin, Vol. ii, p. 285. 

 jGeol and Nat. Hist. Sur. Minn., 2nd An. Rep't. 1873, p. 138. 



