2 THE ILLINOIS GLACIAL LOBE. 



only occasional references to the topography of the drift surface. Appar- 

 ently the first clear recognition of the import of morainic belts in this 

 region was that by Prof. T. C. Chamberlin, who began his investigations 

 in the Wisconsin Survey in 1873, and who in 1876 presented a map, 

 before the Wisconsin Academy of Sciences, showing the distribution of the 

 moraines of eastern Wisconsin. This was followed by one in 1878 show- 

 ing moraines then recognized in the United States. 1 It soon became 

 apparent to Professor Chamberlin that sheets of drift of widely different 

 age occur, the later of which are characterized by stronger morainic lines 

 than the earlier. 



Prior to the recognition of the morainic belts and of drift sheets of 

 widely different ages the published sections of the drift presented many 

 puzzling features. But with this recognition the sections published by the 

 early students became of service in making interpretations. The later 

 students are thus able to build upon the work of the earlier. The disad- 

 vantages under which the earlier students worked, on account of the less 

 complete knowledge of the glacial features, can scarcely be appreciated by 

 those who are furnished with the present facilities for study. Any erroneous 

 interpretations resulting from the restricted acquaintance with such features 

 merit a most charitable construction. For example, the writings of Profes- 

 sor Worthen of the Illinois survey are full of the hypothesis of deposition 

 of the drift by icebergs. The early reports of the geologists of the 

 Indiana survey contain a similar interpretation of the drift. In the light of 

 present knowledge of the moraines, with their attendant valley trains of 

 gravel and other features demonstrating the presence of land ice, the iceberg 

 hypothesis must of course be set aside, but this study of moraines has 

 largely taken place during the fifteen or twenty years since the reports 

 referred to were published. 



The present report is an outgrowth of studies entered upon by Pro- 

 fessor Chamberlin prior to the publication of his paper in the Third Annual 

 Report of this Survey. 2 In that paper it is shown that the State of Illinois 

 is traversed by several morainic lines lying outside the great moraine which 

 is the theme of the paper. These lines, together with others not then 



1 Trans. Wisconsin Acad. Sci., Vol. IV (for 1876-77), 1878, pp. 202-234; with two maps. 

 -Preliminary paper on the terminal moraine of the second Glacial epoch, by Thomas C. Cham- 

 berlin: Third Ann. Rept. U.S. Geol. Survey (for 1881-82), 1883, pp. 291-402. 



