CHAPTEK VII. 



BOUNDARY OF THE GLACIATED AREA IN NORTH AMERICA. 



Doubtless the Ice age both began and ended in a great 

 number of local glaciers which became confluent and con- 

 tinuous only during the middle of the period. One of the 

 most interesting evidences of the independent movement of 

 the different portions of the great North American ice-sheet 

 is to be found in the driftless region of southwestern Wis- 

 consin. Here is an area of several hundred square miles in 

 extent, occupying more or less of the adjoining area in Illi- 

 nois, Iowa, and Minnesota, which remained as an island in 

 the great continental expanse of ice. The ice moved past it 

 upon both sides, and then closed together upon the south, 

 and moved onward, a distance of about 300 miles, to the 

 vicinity of St. Louis. 



When, in the year 1876, attention was first directed by 

 Mr. Clarence King,* Mr. Warren Upham,f and Professor 

 George H. Cook £ to the terminal moraines of southern New 

 England and northern New Jersey, by President T. C. Cham- 

 berlin # to the character and connection of the kettle-mo- 

 raine in Wisconsin, and by Dr. George M. Dawson || to the 



* See my paper in the "Proceedings of the Boston Society of Natural His- 

 tory," vol. xix, pp. 60-63. 



f "New Hampshire Geological Report," vol. iii, pp. 300-305. 

 % "Report upon the Geology of New Jersey for 1878." 



# " On the Extent and Significance of the Wisconsin Kettle-Moraine." 



|| " On the Superficial Geology of the Central Region of North America," 

 from the "Quarterly Journal of the Geological Society," vol. xxxi, 1875. This 

 is a summary of a portion of the author's " Report on the Geology and Re 

 sources of the Forty-ninth Parallel," 1875. 



