190 



completed. The range of elevation four hundred ainetj to five hundred 

 I birty equals forty feel over large areas with places of forty-fi\ e feel or more. 

 A cross profile from bluff to bluff shows these ridge tops to be the highest 

 points between bluffs. Water covering these ridges musl have covered 

 the valley from side to side making a stream of from five to six miles wide 

 and forty to fifty feet deep. Just how much of the year or for how Long 

 periods the water maintained such a volume it would seem impossible to 

 say, but probably the maximum volume was reached in summer and main- 

 tained through the summer months, declining as winter came on. The 

 assumption is that the largest volume of water was produced by the summer 

 melting of the Great lee Sheet that formerly overspread the Northern 

 United States and much of Canada. Whether the west deeper side of the 

 valley was then lower than the terrace portion cannot be stated certainly, 

 deeper water probably covered the part of the valley that now shows the 

 greatest depth. A depth of twenty feet of water is shown for the highest 

 parts of the site of Terre Haute. 



