the water of the ancient lake had passed on its way and had 

 reached the Tippecanoe, a mile further to the west. It was 

 at this time and not until then, that the overflow began on the 

 small dam. The time necessary to destroy this one, although 

 much smaller and retaining a vastly smaller basin of water, 

 must have been very long, even vast, to permit the work 

 that was accomplished by the waves of that long period. When 

 we think of the almost even conflict that is now going on be- 

 tween erosive and constructive forces with the ever deepening 

 drainage lines on one hand and their continued tendency to 

 become obliterated by vegetation, on the other, and the many 

 years needed to show progress on either hand, some concep- 

 tion may be had of the lapse of time between the accumula- 

 tion of the lake body and the final outflow through the eroded 

 dam. Jt is interesting to think that the erosion lines seen 

 now ascending the outlet from the Tippecanoe (See figure 4 of 

 the report), would have crept up the gradient from the river, 

 and succeeded in tapping the lake at the greater dam whether 

 the crest had yielded to the force of the overflow wear or not. 

 However, it would yet take many years for this danger point 

 spoken of to reach the dam and begin its work. The soil of 

 these dams is of course the same existing in the other parts of 

 the morainic uplands of the locality, sand and small gravel 

 being 1 the chief constituents. The measurements and other 

 items of the dams as well as two maps of the same, may be 

 seen in other parts of the report. 



THE LAKE SHORES 



The vegetation of the lake and that of its shores is materi- 

 ially effected by the nature of the soil of its bed and margin. 

 The soil at any point is determined by forces and factors in 

 constant operation, chief among which is the proximity to ele- 

 vated lands. The erosive forces of this area are powerful, 

 both by reason of the rainfalls which are heavy and the nature 

 of the soil which is such as to be quickly affected by water. 

 The amount of detritus removed from the top and side of a 

 hill during the season of heavy rains is enormous, especially 

 when these points are denuded of forests and under-vegetative 

 growth. It is not uncommon to see deep gullies, running to 



18 



