564 



ANNUAL BEPORT SMITHSONIAN INSTITUTION, 1916. 



ing shoals. In the middle section are to be found the well-known 

 Muscle Shoals, around which two canals, aggregating about 150 miles 

 length, with 11 locks, were opened to navigation in 1890, at a cost of 

 $3,191,726. The maintenance of this canal has cost over a million 

 dollars since then. The use made of the canal has never reached its 

 full capacity, but its value has been considerable to Chattanooga and 

 Bridgeport. The completion in 1911 of the 8-mile lateral canal 

 around Colbert Shoals, with its 26-foot lift lock, and the construc- 

 tion of the dam at Hales Bar for power purposes, are the most note- 

 worthy new features of this section. The Colbert Shoals Canal was 

 commenced in 1890 and has just recently been completed at a total 

 cost of $2,320,000. It is 8 miles long and provides for a draft of 

 7 feet. The huge dam at Hales Bar was built by private persons for 

 power purposes, and has a lift of over 41 feet. The problem of foun- 

 dations presented many difficulties, but the work is now practically 

 complete. The foundations are novel in river work in this country, 

 and were made of concrete caissons sunk side by side in the river bed. 

 From these the soft and imperfect rock of the river bottom was re- 

 moved under air pressure and the caisson then " absorbed " in the 

 foundation by filling with concrete. This dam and its appurtenances 

 are said to have cost over $5,000,000, and are planned to provide 

 55,000 horsepower when fully developed (pi. 7, fig. 2) . It is a notable 

 example of the cooperation of private and governmental agencies to 

 secure the fullest development of the river's resources, both in the 

 creation of electric power and the deepening of the river for naviga- 

 tion. Other interesting instances of recent construction are in the 

 Mississippi at Keokuk, Iowa, already referred to, and in the Coosa 

 and Black Warrior Rivers in northern Alabama. In all there has 

 been spent on the Tennessee River a total of $7,393,496, made up as 

 follows: $328,255 in the upper section, above Chattanooga; $6,531,210 

 in the middle section, where the most obstructions exist; and in the 

 lowest section $534,051. The commerce, in five-year periods, in tons, 

 is'as follows: 



Section of river. 



1890 



1895 



1900 



1905 



1910 



1913 



Above Cliattanooga 



Between Chattanooga and Riverton 

 Below Riverton 



77,850 



6,474 



128, 470 



265, 256 

 117,357 

 848,263 



380,607 

 229.160 

 737; 009 



480, 406 

 175,800 

 663,606 



370,430 

 288,750 

 375,570 



474,953 

 315,218 

 272,625 



The Missouri River is the longest tributary of the Mississippi, 

 being 2,551 miles long. Its width is from 300 feet to 1 mile, and its 

 depth over shoals is only about 3 feet. Its banks and bed are easily 

 eroded, and the channels frequentlj^ shift in position. At various 

 times between 1838 and the present shoals have been deepened and 

 snags have been removed from the channel at the worst places, but 



