CHAPTER VI. 



HAMILTON GROUP. 



On the map of Prof. A. Winchell, just mentioned, a belt of the 

 Hamilton group is represented as extending from Wyandotte 

 southwestward through Monroe and Lenawee counties, and on the 

 southwest side of the State another belt is laid down as stretch- 

 ing from the southwest corner of St. Joseph County to the north 

 end of Berrien County. 



In the southern part of Michigan no strata have ever been 

 discovered which could be claimed as representing the Ham- 

 ilton formation, and even if such existed, the belt laid down as 

 running through St. Joseph and Berrien counties would be posi- 

 tively misplaced, as its hypothetical course would be not less than 

 40 or 50 miles further to the southwest. The Hamilton group is, 

 all through Ohio and Indiana, scarcely developed ; in the ex- 

 posures, the beds usually found next incumbent on the Helder- 

 berg limestones are the black shales of Ohio, considered as equiva- 

 lent to the Genesee shale of New York. Only in a few localities of 

 Ohio are some shaly strata of inconsiderable thickness, containing 

 Hamilton fossils, intercalated between the limestone formation and 

 the black shales. 



In the northern part of the Michigan peninsula we find the 

 Hamilton group developed as a heavy formation of over 500 feet 

 in thickness. The southern limit of the surface extent of this 

 group, in the region spoken of, is indicated by a line drawn from 

 Partridge Point, in Thunder Bay, northwestward to intersect the 

 principal meridian in the southern part of Town. 34 ; from there 

 the line goes directly west, through Bear Lake and Pine Lake, and 

 then bends southwest, terminating near Norwood on the shore of 

 Big Traverse Bay. The land-spur across the bay is covered by 

 drift, and presents no outcrops of rock. The continuation of this 

 belt of the Hamilton group, across Lake Michigan and Lake Hu- 



