168 GEOLOGY OF EASTERN WISCONSIN. 



criptions, and in the subsequent treatment of the geological series, 

 large, and it is hoped ample contributions will be made to it, though 

 it will not be always specifically designated, as that would burden the 

 report to the exclusion of other valuable matter. Special estimate 

 should be made for every locality before commencing to sink an ex- 

 pensive well, as there are often local elements that enter into the prob- 

 lem and determine success or failure. It needs also to be borne in 

 mind that even in a favorable locality, failure may result, as the strata 

 are not uniformly porous, and it is possible to bore through a forma- 

 tion that is in most parts highly water-bearing, without striking a 

 vein or seam. Only a single marked instance of this, however, has 

 come to my notice. Failure, also, often results from not properly 

 controlling the water, by the intelligent use of tube and seed-bag, or 

 equivalent apparatus, and by failure to recognize a suitable vein when 

 reached. These and other matters will be found more fully discussed 

 in the general article on the subject in Volume I. 



Bearing these points in mind, and leaving out of consideration the 

 drift system of wells which, from their superficial character and the 

 nature of the formation, have only a local importance, there are three 

 extensive areas over which there is a reasonable presumption tliat 

 fountains may be obtained. 



The first is a belt adjoining Lake Michigan. "Where the elevation 

 is but a few feet above the lake surface, streams will be found, in some 

 eases, in the Niagara limestone, which, if intelligently controlled, will 

 furnish a flow at the surface. This source will be, however, uncer- 

 tain. But by penetrating to the St. Peters sandstone, the probabili- 

 ties of success will be large, and they will be reinforced by the chances 

 lying in the Potsdam sandstone below, though the depth of this 

 will be considerable. Near the lake level, the chances from these 

 sources will be good for the whole of the lake border. From Mani- 

 towoc county southward, they may be said to hold good for elevations 

 not exceeding 100 feet above the lake, and to be fair up to 140 feet, 

 but slight above 150 feet, though perhaps possible in some locations 

 at 200 feet or more. 



The elevations previously given in this report, and the topographi- 

 cal map will show what localities fall within the limits of these con- 

 ditions. The facts connected with the wells already described, and 

 the data given in relation to the several formations, will permit an ap- 

 proximate calculation of the depth, nature of the drilling, and conse- 

 quent cost. 



The second area consists of the Green Bay valley, from Fond du 

 Lac northward. In the vicinity of Lake "Winnebago, a flow from 



