The Misi^ouri River Bluff Debosit. ii 



tttan one per cent, of alumina, or clay, which latter feature please 

 bear in mind. 



As to its origin — that is the aoency through which it was depo- 

 sited—it has been agreed that it is of what is called lacustrian, or 

 lake origin, or in other words it is a sedimentary deposit from 

 suspension in the quiet waters of a lake. Some formerly urged 

 that this material is co-original with that which is recognized as 

 glacial drift ; but there are two objections to that theory, namely, 

 the absence of alumina, or clay, which always characterizes the 

 glacial drift; and, secondly, there is found underlying the bluff 

 deposit the bed of true boulder clay. That it is not, on the other 

 hand, of very lecent origin is proven by the fact that in some 

 localities the tormations known as terraces, belonging to the Ter- 

 tiary Epoch are observed upon its surface, or moulded from it 

 Fossils of the Post Tertiary Period are found in it. comprising 

 almost entirely mollusks, v\hich are closely allied or identical with 

 existing species of fresh water mollusks. 



When these things are all considered, geologists feel safe in 

 concluding that immediately upon the recovery of the country 

 from the allopathic dose of ice which had been administered by 

 the Gods of the North, and while our friend, the Rig Muddy, was 

 fed by such an extreme amount of w^ater IVom the melting ice-sheet 

 as it receded, that it filled a channel so very wide and lake-like as 

 to be scarcely defined as a channel at all, the blufif material was 

 deposited. That the beds were deposited evenly and without a 

 change of level of the country, as some have argued, is proven by 

 the evenness of texture of the material, for you are doubtless all 

 aware that any fluctuation in the velocity of a stream, as affected by 

 a change of the level of its bed, can be certainly detected by a 

 corresponding variation in its sedimentary deposits. The bed of 

 this lake stream, then, it may be decided, was at a constant level. 



These bluffs now constitute long chains, or ridges, parallel to 

 the stream, and observable for many miles along it in continuous 

 chains. This feature becomes less and less prominent as we go 

 back from -the river, and is soon lost in the rolling surface of the 

 prairie. This prominent bluff character along the river is due to a 

 secondary action of the water in eroding, or cutting down through 

 the material after its deposition as the stream shrank and was 

 relieved of some of its detritus. 



Starting from Creston, Iowa, on the line of the C, B. & Q. R. 

 R. we go directly west through this same tier of counties to the 

 river, a dist.nce of about ninety miles, without seeing anything to 

 excite remark or to arouse any suspicion of the existence of the 

 bluff material until we reach the town of Glenwood. 



Here it is that the railroad cuts through the line of the bluffs, 

 and it then runs almost due north between the river and the line 

 to Council Bluffs, a distance of about ten miles, giving one an 



