52 TRANS. ST. LOUIS ACAD. SCIENCE. 



from Bonnet Qiiaire Church down, and several between there 

 and the mouth of Red river ; but until the point at Ellis Cliffs 

 wore away sufficiently to destroy the dam that it caused, there 

 was no knowledge of such a grand effect as that given by Capt. 

 Cowden. 



The last is Scott's, or the shortening combined with the con- 

 centrating theory. Scott proposes to imitate Nature by using 

 the largest timber that can be procured along the river and its 

 tributaries, and by building artificial wrack-heaps, beginning in 

 the slack water at the head of the bend and running them out in 

 curves down from the bend, directing the current from the bend 

 to the point opposite, as shown in the figure. The number of, and 

 distance between, the wrack-heaps will be determined by local 

 peculiarities, the object being to protect the bend from being cut 

 away. Each wrack-heap will begin at the bank in the slack 

 water caused by the one above, in order to prevent the cur- 

 rent from getting behind and cutting the bank. Thus b}' gradu- 

 ally shortening the bends the whole river will be shortened, 

 increasing its average fall and its scouring capacity, causing it to 

 cut a deeper bed for itself, and thus gradually doing away with 

 the necessity for levees, and permitting finally a permanent drain- 

 ing of the swamps. 



The artificial wrack-heap is based on the natural action of the 

 river where the banks are covered with timber, and was suggested 

 to the writer by observations made on the wrack-heaps that have 

 been built by the river itself, as at Island i6. Devil's Elbow, and 

 Islands 66 and 82. At the places named wrack-heaps have been 

 formed by the river, and they have effectually resisted the cur- 

 rent, forcing the channel across the river and forming a bar below 

 until the shore above was cut away, and, allowing the current to 

 get behind them, they were gradually left on the opposite side of 

 the river. 



The wrack-heap if properly fastened is immovable, and if con- 

 structed in proper places is practically indestructible. 



The difference between the wrack-heap dyke and any solid 

 dyke, whether of stone, timber piles and willows with stone 

 ballast, or earthen embankments, is, that it is cheaper and more 

 permanent than any other that will allow the current during high 



