158 GEOLOGY OF EASTERN WISCONSIN. 



six miles to the west. Now between Ripon and Fond du Lac, along 

 a parallel and not distant line, the dip of the lower face of the Tren- 

 ton limestone is accurately ascertained to be 23 feet per mile to the 

 eastward. Calculating upon the basis of this dip, and making allow- 

 ance for the drift, there should be less than fifty feet of the Trenton 

 limestone at the location of the well on Algoma street. 



This result is confirmed by calculations based on different data, and 

 by a general inspection of the problem. Assuming this to be correct, 

 the thickness of limestone below is sufficient to occupy the whole 

 horizon of the St. Peters sandstone and Lower Magnesian limestone; 

 or in other words, the 208 feet of limestone in the one case, and the 

 240 feet in the other, just about fill up the space that we should ex- 

 pect would be occupied by the Trenton, St. Peters, and Lower Mag- 

 nesian formations. What then has become of the St. Peters sandstone? 

 One of the more recent discoveries of the survey makes this perfectly 

 clear. The upper surface of the Lower Magnesian limestone in this 

 region is very undulating; we might say, billowy. The St. Peters 

 sandstone lies in the troughs between these billows, and usually cov- 

 ers their crest, but sometimes the Trenton rests directly upon the 

 elevated portions of the lower limestone, and the St. Peters sandstone 

 is entirely wanting. This has actually been observed in some cases, 

 and drilling at other points has left no doubt that this is not an un- 

 common fact. If we suppose then that the Trenton limestone here 

 rests directly on the Lower Magnesian as it does near Ripon, the 

 whole of the difficulty disappears. See Plate YI. 



The calcareous material found in the sandstone below, doubtless 

 represents the Mendota limestone, and must be regarded as confirm- 

 ing the above conclusions. 



The well at the Hospital discharges about 22,000 gallons per day. 

 This, accepting the foregoing views, is derived from the Potsdam 

 sandstone, below the calcareous Mendota stratum. Its collecting area 

 is probably twenty-five miles to the northwestward, and has but a 

 slight elevation. 



At the mill of W. N. Davis, on the shore of lake Winnebago, in 

 Calumet, are two fine wells, giving a copious flow of clear, cold, 

 sparkling w r ater, impregnated with considerable iron and some sul- 

 phuretted hydrogen. The proprietor gave the depth as about 90 feet, 

 but was not certainly informed whether rock was reached or not, as 

 the well was not sunk by him. These are probably to be classed with 

 f he Taycheedah wells, having their source to the east, though it is not 

 impossible that they belong to the Oshkosh system, as the fountains 

 surrounding the lake indicate that its bed is impervious. 



