INTRODUCTION. 3 



known, have been mapped in detail and a large amount of data concerning 

 them have been collected. 



The detailed studies were begun in the spring of 1886, and the follow- 

 ing statement concerning them was made by Professor Ghamberlin in his 

 report to the Director for the fiscal year 1886-87: 



Messrs. L. C. Wooster, R. D. Salisbury, F. Leverett, and myself have under- 

 taken a work that is measurably new, though a part of the general plau of work 

 previously inaugurated. In the region about the head of Lake Michigan and between 

 it and the Erie basin is a tract which was invaded by successive glacial movements 

 from both these great basins, these movements being more or less inharmonious and 

 conflicting, resulting in exceptionally complicated phenomena. There arose from this 

 a need for detailed study and the development of more refined methods of investiga- 

 tion than those demanded by the simpler drift tracts. 1 



During the held season of 1886 the study was extended out for a dis- 

 tance of 50 to 100 miles from the head of Lake Michigan in Illinois and 

 Indiana, a division of the district being made so that each person worked a 

 separate area. Since that season the field work has been largely carried on 

 by Professor Salisbury and the writer, though Professor Chamberlin has 

 constantly superintended the work and has from time to time visited the 

 field. Professor Salisbury's work, since the first season, has been largely 

 in southern and western Illinois, while the writer's has been mainly in the 

 northern half of the State. During the autumn of 1892, however, the 

 writer was detailed to collect soils and prepare a soil map of Illinois for the 

 Illinois Board of World's Fair Commissioners. This study necessitated a 

 reconnaissance of the southern portion of the State. This reconnaissance 

 has been supplemented by more detailed studies in 1894 and 1896. The 

 field work carried on by the writer in the region under discussion has 

 been done mainly in the field seasons of 1886, 1887, 1892, 1894, 1896, and 

 1897. In the intervening years the same line of study was extended into 

 bordering districts, and the broadening of the field has resulted in a better 

 understanding of the features of this region. In the preparation of this 

 report, and also throughout the field study, Professor Chamberlin has given 

 constant advice and direction. The report really embraces the information 

 obtained by Professor Chamberlin in his early reconnaissances, and the best 

 fruits of his wider studies, and of the studies of his other associates, as well 



'Eighth Ann. Rept. U. S. Geol. Survey (for 1886-87), 1889, p. 141. 



