156 GEOLOGY OF EASTERN WISCONSIN. 



The shallower system of Artesian wells at Oshkosh is quite similar 

 to that of Fond du Lac, already described. They vary in depth from 

 15 to 100 feet, and derive their flow variously from within the drift, 

 at the surface of the rock, and at varying depths within it. The 

 source of their supply is undoubtedly to the westward and less than 

 ten miles distant. 



The deeper wells possess unusual interest from the facts they de- 

 velop relating to the strata beneath. Unfortunately no complete 

 record of the formations passed through in sinking the well at the 

 Northern Hospital for the Insane seems to have been made, and noth- 

 ing is now available but the very general statements of the person 

 who drilled the lower portion, and an inspection of the mingled drill- 

 ings at the well. These showed that variously colored sandstone 

 strata had been penetrated to a considerable depth, and that a reddish 

 granitic rock had been entered. 



The following items were furnished by Mr. J. H. Johnson, who 

 drilled the lower portion : 



Struck limestone at 60 feet. 



" sandstone at 300 " 



" waterat .'' 800 " 



" red sandstone at 540 " 



" white sandstone at 585 " 



granite at 714 " 



T/hite granite at 935 " 



Bottom 961 " 



Mr. Johnson expressly stated that below 300 feet it was all sand- 

 stone till the granite was reached. 



In regular order we should expect in descending, Trenton lime- 

 stone, the St. Peters sandstone, the Lower Magnesian limestone, and 

 the Potsdam sandstone, including a calcareous stratum, and the gran- 

 itic rocks at the bottom as found. The question is naturally sug- 

 gested. Is the St. Peters sandstone wanting, bringing the Trenton 

 and Lower Magnesian limestones together ; or is the Lower Magne- 

 sian limestone wanting as such, bringing the St. Peters and Pots- 

 dam sandstones together? 



Much light is thrown on this interesting question by the very excel- 

 lent record and the drillings of a public well, subsequently sunk within 

 the city of Oshkosh, preserved by Mr. K. M. Hutchinson, and sub- 

 mitted to me by the kindness of Dr. Lapham. 



The record is incorporated in my notes, on an examination of the 

 drillings, which are as follows: 



