lo The West American Scientist. 



THE MISSOURI RIVER BLUEE DEPOSIT. 



I have been asked to speak to you of some of the more distinc- 

 tive features of Western Geolooy, and have decided to talk to-day 

 of what is known as the 'Bluff Deposit' of the Missouri River 

 valley. This deposit is to be observed, and has been studied 

 along some other rivers of our central system, and yet it reaches 

 its greatest development and possesses the greatest interest along 

 this valley, so we will confine ourselves to the ' Big Muddy,' if 

 you please. 



It has been my privilege to make a rather thorough study of 

 the formation as it is exhibited at Council Bluffs, Iowa, and on 

 down the river to Kansas City, and this article will be written 

 partly from my own observations and partly from the work of our 

 various geological surveys. 



This bluff system differs radically from what is usually known 

 by that name along the valleys of rivers in other parts of the 

 country, both as regards its origin, its chemical composition and 

 physical character. 



Whenever a stream of water, free from too great an admixture 

 of sedimentary material, begins to flow over the surface of the 

 earth, the natural tendency is to form a bed by cutting down into 

 the earth, to deepen and at the same time narrow the channel 

 This is due to what is called the erosive power of the water, and 

 the rapidity of its action depends upon the velocity of the current 

 and the character of the material through which the bed is cut. 



Start at the bed of any well marked stream and as you go back 

 from the stream you will find the banks of the valley rising as they 

 recede, and in very many cases you will be able to mark the 

 higher levels that have constituted the river bed at successive 

 stages of its growth. These modelings of the surface and rocky 

 bluffs, due to the. erosive power mentioned above, constitute what 

 is generally known as the bluffs of our river systems. 



The Missouri river steps in here and asserts its independence of 

 all established custom, renounces its adherence to fashion, and 

 founds a system of bluffs upon a new plan. Instead of being the 

 result oi erosion, these bluffs have been produced by a process of 

 accretion and deposition of sediment. 



The exact origin of this sediment has been disputed by the 

 many geological authorities who have studied and published it, 

 but it is recognized as a formation equivalent to the J.oess of the 

 Rhine and other European rivers. Dr. Owen called the material 

 a 'siliceous marl.' and others 'siliceous loam.' Prof Swallow, 

 of Missouri, applied the name ''bluff," which is accepted in lieu of 

 something more satisfactory from a strictly scientific point of 

 view. 



The composition of several specimens of the material taken in 

 Iowa, according to Prof. Emery's report (Geology of Iowa, 1870) 

 is about '62% of silica, (^% of carbonate of lime, 3^^' of iron and less 



