226 Wisconsin Academy of Sciences, Arts, and Letters. 



Dr. E. Hitchcock refers to these accumulations in his report on 

 the geology of Massachusetts/ and classes with them " diluvial 

 elevations and depressions, " occurring at other points in that and 

 adjoining States. It would appear, from the geological reports of 

 the Eastern States that analogous, though not certainly identical 

 formations, occur locally, more frequently than in the interior, 

 and this, from the mountainous nature of the country, is not 

 strange; but no continuous massive range seems to have been 

 discerned, except the southern one already described. 



In the interior, so far as yet ascertained, the drift limit is not 

 marked by any such persistent ridge-like accumulation, but grad- 

 ually dies away or is buried by later deposits, so that the precise 

 limit of glacial advance is not easily determined. The only ap- 

 proach to an exception to this, known to me, is the case of the 

 Kettle moraine in Central Wisconsin, where it lies near the border 

 of the driftless area. Elsewhere around that area, the drift thins 

 out very gradually, so as to render the mapping of its margin a 

 work of close inspection ; and, as the region presents no evidence 

 of subsequent submersion, or any other special modifyi ng agency^ 

 except the usual meteorological forces, this would seem to repre- 

 sent approximately the original form of deposit. 



It is evident from the foregoing sketch that much observation 

 remains to be made before the complete geography of this forma- 

 tion is determined. The conjectural lines on the map are only 

 theoretical suggestions, preliminary to observation. 



Summary. — It may be helpful at this point to summarize, and 

 bringinto close juxtaposition, in thought, the leading characteristics 

 of this remarkable formation. 



1. Its linear extent is very great, whatever its final limits may 

 be found to be. 



2. It has a width of from one to thirty miles. 



8. Its average vertical thickness can only be very roughly esti- 

 mated, but may, very prudently, be placed at 200 or 300 feet. 



4. Its surface configuration is peculiarly irregular, and denotes 

 an extraordinary origin. 



1 Geol. of Mass. 1833, pp. 144 et seq. 



