CORRELATION OF RAISED BEACHES 



415 



fidence, and thus to reconstruct the water planes of the extinct 

 lakes. 



CHARACTER OF THE RECORD 



On the rocky and exposed peninsula north of Sturgeon Bay the 

 shore-lines are developed in conspicuous form. Fig. 2 shows a char- 

 acteristic headland cut by the waves at successive levels so as to look 

 like a great flight of steps. Heavy beach ridges of cobble stones occur 

 across the bay heads or on shelving shores (see Fig. 3). The record of 



Fig. 3. — Beach ridge of the Nipissing shore-Hne at Graceport, near Sturgeon Bay. 

 It stands 19 feet above the level of Lake Michigan. On the left, between this beach 

 and the shore of Green Bay, are lower ridges. 



successive stages is singularly complete in this district, because exposure 

 was great enough to allow each successive water-plane to be registered, 

 while the rocky surface was usually too resistant to allow the shore 

 cliffs of a lower lake stage to be cut back beyond higher shore-lines, 

 and thus to destroy them. 



South of Sturgeon Bay the expression of the beaches undergoes a 

 marked change, corresponding to the change in the character of the 

 ground. In place of bed-rock at the surface, there are thick red-clay 

 deposits, in part ice-laid and in part water-laid, into which the waves 



