336 GEOLOGY OP EASTERN WISCONSIN. 



The term Guelph has been applied to the uppermost beds on ac- 

 count of a similarity of fossils to those of the Guelph limestone of 

 Canada, to which the Wisconsin formation is probably equivalent. 

 The recognition of this equivalence is duo to Prof. Whitfield. 



The Racine beds are the equivalent of what has been known as 

 the Eacine limestone,* except that the upper portion is now separated 

 as Guelph, and the reefs and associated rocks west of Milwaukee, 

 which have been referred to a lower horizon, are included in it. 



The lowest strata of the Niagara series are named Mayville beds 

 because they have their maximum development and finest exposure 

 south of that village. For the strata that lie between these and the 

 Eacine beds, in the southern part of the state, the term Waukesha 

 limestone, which has been previously applied to a portion of them, 

 has been adopted with modifications. The white limestone, that lies 

 upon the Mayville beds, in the northern portion, receives its name 

 from the township of Byron, where it is extensively utilized for lime, 

 building stone, and flagging, and where occurs the only fossil yet 

 found abundantly in it. The Upper and Lower Coral beds have been 

 thus designated from the prej)onderance of coralline forms among 

 the fossils found in them. 



The accompanying plates (Plates XII and XIII) will show the po- 

 sition and relations of tliese subdivisons very satisfactorily. Plate 

 XIII is based upon the facts developed in sinking the Artesian wells 

 at Sheboygan, Milwaukee and Western Union Junction. They were 

 sunk after my investigations upon this formation, and confirm in a 

 most satisfactory manner my conclusions. The plate also illustrates 

 a number of other interesting geological facts, among which is the 

 northward dip of the strata. It also furnishes valuable data in ref- 

 erence to Artesian wells. 



MAYVILLE BEDS, 



As already indicated, these beds form the lowest member of the 

 Niagara series throughout its whole extent. They possess the same 

 general character throughout their entire area, and, in this respect, 

 differ from the rest of the group. The rock of this member is, in 

 general, a rough, coarse, gray, magnesian limestone. There is consid- 

 erable difference, however, among the several layers that compose it, 

 and some of these maintain their peculiarities with great persistency, 

 so that it is possible to distinguish them at points one hundred miles 

 or more apart. This makes it possible to describe a section which 



' Geology of Wisconsm, 1862, p. 67. 



