SCOTT IMPROVEMENT OF THE WESTERN RIVERS. 53 



water to flow over it. The current passing through the intersti- 

 ces of the branches prevents entirely the reacting eddy, which is 

 so destructive to solid dykes of any kind that do not rest on a 

 soHd foundation. In passing through the branches, the current 

 is retarded in its flow, and, as velocity is an important factor in 

 carrying sediment, the retardation causes deposits below and 

 "behind the wrack-heap, and a bar is formed, which in turn rein- 

 forces and strengthens the wrack-heap. The combination of the 

 two forces the water in a new direction. 



The wrack-heap can be built at all stages of the river, except 

 during ice ; but high water is the most favorable, and spring and 

 early summer the best time, as in high water there is most sedi- 

 ment, and during early summer the leaves are thicker and stronger 

 on the trees, and would form an important factor in resisting the 

 flow of the current. 



The cost of the wrack-heap dyke would be so small in com- 

 parison with any other that has been oflered, that it looks ridicu- 

 lous ; whilst the time required to construct them is so short, that, 

 if at once adopted, the present generation might expect to reap 

 some of the benefits. 



To sum up the whole ai'gument in four propositions, we assert : 

 First — That neglect of the river means the destruction of naviga- 

 tion, agriculture, and health. Second — An expensive system 

 means no system. Third — A wrong system means failure. 

 Fourth — A proper system means prosperity in all directions; 

 for as the farmer is protected, the transportation of his products 

 gives employment to commerce, and health encourages immi- 

 gration. 



EXPLANATION OF THE PLATE. 



1. End view of single line of trees in from 6 to 20 feet depth of water. 



2. End view of double line of trees in from 20 to 35 feet of water. 



3. End view of triple line of trees in from 35 to 50 feet or over. 



4. Rock anchors fastened to trees by iron rods connecting with bolts fastened in the tree 



and rock. 



5. Bottom of river. 



6. Banks of the river. 



7. Sandbars. 



S. "Tow-head" where there are two channels, causing shallow water in both. 

 9. Short spur dykes that protect the shore and give direction to the current. 

 a I. A perpendicular view of single row of trees in dyke. 

 « 2. A perpendicular view of double line of trees in dyke. 

 a 3. A perpendicular view of triple line or more in dyke. 

 The arrows show the course of the current. 



