ARTESIAN WELLS. 



465 



some of the Fond du Lac wells pours forth with such strength as to make a little 

 rivulet, and might, if confined, be raised many feet. They find it necessary to tube 

 the hole only a few feet down, as the clay keeps its place well. The water is 

 excellent for drinking, and tolerably soft. The base rock at Fond du Lac, and 

 probably at Oshkosh, inclines to the southward. The reservoir in these cases is in 

 the coarse gravel that covers the lime-rock, confined by the impervious clays above. 

 The country on the southeast rises rapidly in a bluff of two hundred feet, composed 

 of lime-rock, against which the clay and drift abut. On the south and southwest, 

 the surface rises more gradually ; and on the north and northwest, the rise is still less. 

 The surface of the Lake is lower than the top of the wells, so that the supply must be 

 looked for in the adjacent country, and we must also suppose that there is no con- 

 nexion between that source and the Lake ; for if there was, it would discharge there, 

 and rise no higher. The clay doubtless forms the bed of the Lake, about the southern 

 half, and is not penetrated by its waters. If such was the case, the temperature of 

 the adjacent wells would be expected to change with the temperature of the Lake. 



The sections of the red clay shown by these borings, and some others, taken at 

 the bank of the Lake, and at various bluffs, separated one hundred and fifty miles 

 from each other, prove that here, as on Lake Superior, there are bands and 

 strata of sand and gravel, intermingled with the red clay. Here, as there, boul- 

 ders are scarcely ever seen resting on the clay ; that is, where the clay is the 

 surface material ; and also, that the high drift ridges are composed of coarse mate- 

 rials, and support boulders of Plutonic rocks.* The drift-hills between Sheboy- 

 gan and Fond du Lac are, by estimate, three to four hundred feet above Lake 

 Michigan. They are composed mostly of limestone, very coarse gravel, and chert, 

 but with occasional pieces of quartz and other igneous rocks. The boulders are 

 quartz, syenite, granite, greenstone, black and red trap, hornblende, augite, and 

 limestone. As you rise above the red clay, the wells along the road indicate a gra- 

 duation into a whitish, marly clay, that gives a very strong soil. The drift-hills 

 no doubt overlie the red clay. They show large tracts of country, covered by 

 steep conical pits, without water, that are called " potash kettles," twenty, fifty, 

 and eighty feet deep. 



In the red clay banks on the east shore of Lake Winnebago, three miles north of 

 Tayhedah, are beds of limestone and gravel, intermingled with the clay. The 

 shore of Lake Michigan, from Milwaukie to " Death's Door," exhibits the stratification 

 of this deposit very satisfactorily. 



At Milwaukie, it rests on coarse gravel drift. At Sheboygan, at the waters edge, 

 we find — 



Feet. 



1. Red clay, "hard pan," with half-worn pebbles of granitic rocks 



and cherty limestone (springs of water along the upper 



edge), . . . . . . . 20 to 25 



2. Sand and small gravel, . . . . 10 to 15 



3. Coarse yellow sand forming the surface — -thickness irregular. 



* On the low red clay ground between Oshkosh and Neenah there were more boulders of northern rocks 

 resting on the clay than were seen anywhere else. 



59 



