changes, not in a haphazard manner, but according to well 

 defined laws. In all the processes of erosion there is no more 

 potent factor than that of vegetation. Regarding that many 

 things may be cited. The peat deposits add greatly to the 

 rapidity with which lakes and swamps are filled, while the 

 plant covering of the hills on the contrary, greatly retards the 

 erosive processes. As a consequence of all these topographic 

 changes the soils and slopes must change; so that the plant 

 societies which are replaced in turn by others, are adapted to the 

 new conditions. 1 ' It will be at once seen that there are mutually 

 powerful agencies at work in an area like this of pronounced 

 topography and strong- vegetative influences. The erosive 

 influences are all but balanced by the constructive work of veg- 

 etation. Among the various types of elevations, the esker, 

 then represents a unit both topographically and ecologically. 

 It possesses on its surface trees and undergrowth ranging from 

 xerophytes to mesophytes. Within 150 paces, crossing its 

 crest transversely, one passes from the scrubby black oaks, 

 representing the xerophytic side, to groups of lindens and wal- 

 nuts representing the mesophytic side. With its elevation 

 of sand and gravel the esker furnishes the necessary condi- 

 tions of exposure and protection from the rigors of heat and" 

 cold and moisture, which determine the vegetative types of 

 its surface. What is here true of the esker is true of other 

 elevations provided that they are of the same soil. A clay hill 

 will differ in its vegetation from one of sand or gravel. How- 

 ever, the topographic relations are more important than the 

 geological, and hence one will observe that the change in. 

 vegetation is only a modification. 



The vegetative influence on the entire topography is very 

 marked. Located in the belt of heavy rainfall, with an abun- 

 dance of water in the ground from spring's, and in the air from 

 evaporation of the lake's surface, the entire ground surface, 

 with the exception of certain elevations, is covered with a 

 rich herbaceous vegetation and the hills with dense forests. 

 Wherever interfered with the forests are not luxuriant but 

 where primeval they are grand in their thickness and deep 

 shade. One stretch of elevation on the 20 foot contour line, 

 and back from the lake shore a half mile, proved a magnificent 

 sight. The trees, nearly all mesophytes, were lordly monsters. 



9 



