NATIJEAL WATERWAYS IN THE UNITED STATES — HARTS. 557 



in 1903 and completed in 1908. The work of dredging the channel 

 has been about four-fifths completed. Of 18,000,000 cubic yards of 

 dredged material which had to be removed in 1905, less than three 

 and one-half million yards now remain. The original depth of 9 feet 

 has now been increased to 31 feet. 



THE OHIO RIVER SYSTEM. 



The Ohio Eiver is the most important tributary of the Mississippi, 

 and, indeed, it is the most important river of the country as a com- 

 merce carrier. In point of tonnage Pittsburgh has the largest 

 commerce of an}^ inland river port. This river, like all those of the 

 Mississippi Basin, was originally shallow, crooked, obstructed by 

 sand bars, and has always been subject to wide variation of dis- 

 charge. Work was done on this stream, originally, as early as 1827. 

 Snagging, rock removal, and bar scraping were first tried, and later 

 the channels were deepened by placing wing dams at important 

 places to afford a 6-foot channel depth. Notwithstanding consider- 

 able success in this direction, this did not meet all the requirements 

 of navigation of late years, for new shoals would be formed in high 

 water, and the uncertainties of open river regulation made the navi- 

 gation precarious at low stages. But as work progressed the river 

 channels became more reliable, and an enormous commerce, princi- 

 pally in coal and lumber products, grew up, owing to the favorable 

 location of the stream, running as it did between the coal centers in 

 western Pennsylvania and the large cities along the Ohio and 

 Mississippi Rivers. A terminal harbor at Pittsburgh was soon 

 needed. In order to more easily reach the important coal mines and 

 to provide a quiet port in which loaded coal barges could be stored 

 during low water in large numbers ready for flood stages on which 

 they could move downstream, a dam in the upper part of the river 

 was necessary. In 1877 one was built, and the success which this 

 had led to the construction of several others lower down in 1890, 

 until in 1910 a project was adopted for the canalization of the entire 

 Ohio River, with locks and movable dams throughout its length of 

 about 1,000 miles (pi. 3, fig. 2). This project is to provide a depth of 

 9 feet and is now being constructed, 14 locks and dams having been 

 completed, 4 will be finished during 1915, and 13 are now imder con- 

 struction. The estimated cost of the new project is over $64,000,000 

 and is one of the most comprehensive plans of river improvement 

 ever undertaken in this country. The plan provides for 54 locks, 

 with single-leaf sliding gates instead of swinging gates (pi. 4, fig. 1), 

 and includes dams having bear trap sections (pi. 4. fig. 2) and mov- 

 able wicket sections (pi. 5, fig. 1) so arranged as to furnish pools hav- 

 ing 9-foot channels at low stages, with all dams up. As the water 



