31 



1. Terraces (A) and (B) in the gorge of the Whitewater River 

 (mainly below the city of Kichuiond), were developed by the stream 

 at periods, in each ease, when its gradient was very mnch less than 

 at present ; a gradient sutticiently low to permit it to erode chiefly 

 laterally. 



2. In the case of the npper terrace, at least, this period of lateral 

 erosion was interrupted by a relative elevation of the land (bed 

 rock), which was not uniform, but increased southward from the city 

 of Iiichniond to an undetermined distance. The total amount of the 

 movement as indicated by terrace (A), is not less than 10 feet of ele- 

 vation per mile in a general southward direction. 



?.. Since the terraces along each of the three forks are composed 

 very largely of glacial material, it seems probable that temporary 

 ponding of waters, and variation in amounts of water and sediment 

 present, are largely responsible for their presence and for their rela- 

 tive positions. It seems probable also, however, that diastrophic move- 

 ments may have had some part in producing the lack of parallelism 

 in surface gradient of terraces of the different series. 

 The time relations involved can be stated clearly only in part. For 

 example, the lowest terraces along the three forks, such as (1) along the 

 West Fork, nuist be of date so recent as to fall within the category of 

 present-day formations. Others, such as (A) in the gorge, must evidently 

 be considered as belonging to a period sufficiently remote to allow for the 

 erosion of a channel in bed rock flOO to SOO feet in width and 64 feet deep. 

 Geologically this is still, however, quite recent, and this work may all 

 have been accomplished since the final withdrawal of glacial ice from this 

 latitude. 



Earlham College, 

 Richmond, Indiana. 



:— 20034] 



