4 THE ILLINOIS GLACIAL LOBE. 



as the data directly obtained by the writer. It is with gratitude as well as 

 with pleasure that this acknowledgment of indebtedness is made. 



In this investigation there have been several distinct lines of observa- 

 tion, which supplement one another in throwing light upon the glacial 

 succession. (1) The work began with a mapping of moraines, and this map- 

 ping has been carried to completion, i. e., each moraine has been followed 

 throughout its entire course with sufficient zigzagging to learn its breadth 

 and general features as well as the position of the crest. (2) With this 

 study of the moraines there has been carried on an investigation of the 

 stratigraphy of the drift, shown by well sections or other exposures, both 

 artificial and natural. Several thousand well sections have been collected, 

 man)- of which appear in tabulated form in this report. The mode of 

 deposition of the glacial drift is such that a simple study of the drift sheets 

 in a vertical series can not, in many cases, furnish index of the glacial suc- 

 cession. The mapping of the moraines has often aided greatly in working 

 out the full glacial succession. (3) Coupled with the stratigraphic study 

 and the mapping of the moraines there have been a few measurements and 

 estimates of the relative amounts of erosion or other surface changes in the 

 drift in different parts of the drift-covered area, a study which aims to throw 

 light upon the relative ages of different drift sheets. 



Since the townships are frequently referred to by number and range, 

 rather than by the civil name applied to them, a brief explanation of the 

 method of numbering townships in this region is here presented, together 

 with a map (PI. II) showing base lines and principal meridians. The expla- 

 nation begins with the Second Principal Meridian adopted by the United 

 States Land Survey, since the First Principal Meridian (which follows the 

 State line of Ohio and Indiana) was not used as a basis for laying oxit unj 

 portion of the region under discussion. 



The Second Principal Meridian leads north to south through west- 

 central Indiana from the line of Michigan to the Ohio River, and is situated 

 about 2 miles east of longitude 86° 30' west from Greenwich. The base 

 line crosses the southern portion of Indiana within 1 or 2 miles south of 

 latitude 38° 30'. The townships are numbered both north and south from 

 this base line. The State of Indiana only extends to T. 9 S., but reaches 

 T. 38 N. of the base line. The ranges are numbered both east and west 

 from the Second Principal Meridian. Those on the east extend to the State 



