Masterpieces of Science 



river finding a shorter way downward to the sea, 

 leaving its former circuit as a great pool, or 

 moat, as it is called by the common folk along 

 the banks of the Connecticut River. It often 

 happens in the lower Mississippi that the course 

 of the river around the promontory of the ox-bow 

 is ten or more miles in length, while the space 

 across the neck is less than a mile in distance. 

 When the river finally breaks across the neck 

 the whole system of rebounds of its current 

 against the banks, from the point of change 

 downward to the mouth, may become altered. 

 The points which before were in process of erosion 

 may become the seats of deposition, and those 

 which previously were gaining may begin to 

 wear away. In this manner a river, in time, 

 wanders to and fro across its whole valley, taking 

 material from one side, sorting it over, removing 

 that part which is fine enough to be borne away 

 by the current, and rebuilding the remainder 

 into the alluvial plains. 



We are now prepared to consider a very 

 peculiar and most important function which 

 these alluvial plains perform in the physical life 

 of the earth. In such a valley as the Mississippi, 

 we have probably not less than fifty thousand 

 square miles of alluvial plains which have been 

 formed of the waste removed from the rocks in 

 the torrential portions of the streams in the 

 mountains and hill districts of the valley. This 

 alluvial material is, on the average, not less than 

 fifty feet thick. It is therefore equivalent to 

 150 



