232 Wisconsin Academy of Sciences, Avis, and Letters. 



stage of its activity, and separating the formations on either hand? 

 by a chronological barrier. It is manifest that the true Boulder- 

 Clay, or ground moraine, south of the belt, must have been formed 

 earlier than that north of it, and that the two portions are not at 

 all synchronous. In sedimentary formations synchronism is found 

 in horizontal strata, but in glacial deposits it is to be sought in. 

 linear belts, concentric with the margin of the glacier. This fact 

 finds illustration, and emphasis, in the demarcation introduced by 

 this singular corrugation of the wide-spread glacial sheet. It is 

 difficult to limit the value of such a determinate line, in the midst 

 of the complex drift formations, if fully established, and should 

 similar belts be found to mark other stages of glaciation, there 

 would be opened a definite line of investigation that promises 

 much assistance in unraveling the gnarled skein of Quaternary 

 history. 



While it does not follow, necessarily, that all formations over- 

 laying the true glacial clay, south of the Kettle moraine, are older- 

 than those occupyiog similar relations to the newer Till, north of 

 it, it is clear, that similarity of stratigraphical sequence is not, by 

 any means, sufficient ground for assuming chronological equiva- 

 lence. It is evident, that all endeavors at correlation between the- 

 superficial deposits, on the opposite sides of the moraine, should 

 be attempted with much circumspection. 



These suggestions have especial application to the discussion of 

 the vegetal deposits, so frequently found in the later Quaternary 

 formations. By many writers, the various deposits of this kind,, 

 in the Mississippi basin, have been, very naturally, in the present 

 state of our knowledge, grouped together without reference to the 

 necessary discriminations above indicated, and, as a result, beds 

 of diverse age are referred to a common stratum. A general dis- 

 cussion of these deposits is not sufficiently germane to our sub- 

 ject to be fittingly introduced here, but it is appropriate to point 

 out the fact that some of the vegetal strata sustain such a relation^ 

 to the Kettle moraine, that they must be widely separated from 

 others, in the date of their accumulation and burial. Some of 

 these organic strata lie at the immediate foot of the moraine, be- 

 neath fiuviatile and lacustrine deposits that^ I am confident,, begaa 



