GEOLOGY OF EASTERN WISCONSIN. 



of them are rather to be conceived as streams, issuing from the rock 

 full fledged, than as the bubbling source of a rivulet, implied by the 

 term spring. In some places they furnish, without further augmen- 

 tation, sufficient power for efficient flouring mills. In one case two 

 mills are supplied by using the water in succession, within one-half 

 mile of the source. 



The quality of the water of this class varies more than that of the 

 preceding, owing, as it may be conjectured, to the greater or less 

 effect of the shales upon it. These contain organic matter, iron py- 

 rites, and other ingredients which on exposure indicate their unsta- 

 ble chemical nature, by changes of color and otherwise, and, by so 

 doing, warrant the belief that they sometimes make unfavorable con- 

 tributions to the stream in contact with them. The water of most of 

 them, however, is clear, cool and refreshing, and in character very 

 similar to those of the preceding classes, though' somewhat harder, on 

 the average. Several are supercharged with lime salts, which are de- 

 posited as travertine about the spring, on the escape into the atmos- 

 phere of the carbonic acid which held them in solution. The tem- 

 perature is also varying, being dependent of course upon the thick- 

 ness of the limestone above. 



Above this generous horizon there is no well marked water-bear- 

 ing stratum of rock, although there are numerous fine springs issu- 

 ing at various points from the Niagara limestone. The widely known 

 Waukesha springs are examples. Druecker's spring, near Ozaukee, 

 and several fine ones near Sturgeon Bay, belong to a similar geologi- 

 cal position. 



The foregoing are all derived from rocks that were laid down under 

 the ancient Silurian ocean, rocks whose ages are to be reckoned by 

 myriads of years, and from which there has at least been a liberal al- 

 lowance of time for the removal of whatever soluble matter may have 

 been originally incorporated in them ; and yet we find in all that have 

 been analyzed, varying quantities of the oceanic salts. The remain- 

 der issue from loose material of much more recent origin, formed by 

 the agency of ice and fresh water, so far as the evidence goes; and 

 yet, as this material was derived from the preceding oceanic forma- 

 tions in great part, the same ingredients may and do occur in the 

 water. They are as a class more superficial than the preceding, and 

 more liable to contamination from surface impurities, and for a like 

 reason their temperature is often less constant and their flow less reg- 

 ular. While this is true, some magnificent springs belong to this 

 class. It will not be necessary to enter so much into detail here, as 

 in many cases the water-bearing stratum is merely local. 



