NATURAL WATERWAYS IN THE UNITED STATES HARTS. 551 



These improvements have had a marked influence on freight and 

 freight rates. In 188.5 the tonnage through the St. Marys locks was 

 3,256,628 tons, valued at $53,413,472. In 1912 the traffic was 72,472,- 

 676 tons, valued at $791,357,837. The average of the five years 

 1881-1885 was 2,399,310 tons, and for the five years 1908-1912 was 

 57,519,763 tons, an increase of nearly twenty-four fold. The average 

 distance that this commerce was carried was over 800 miles. The 

 improvement in the channels since 1900 has enabled vessels to be in- 

 creased in size from 8,000 tons to 13,000 tons, and the cost of trans- 

 portation has been reduced from 1.18 mills per ton mile, in 1900, to 

 0.67 mill per ton mile, in 1912. It was estimated that the traffic 

 passing the St. Marys Kiver locks in 1912 amounted to upward of 

 sixty billions (60,000,000,000) of ton miles, and it was asserted that 

 the saving in freight of 0.51 mill per ton-mile was directly attribu- 

 table to the channel improvements. It is worthj^ of note that the 

 eastbound traffic greatly exceeds that bound westward, and that it 

 is mainly bulk freight and mainly through traffic. Over one-half 

 of it is iron ore and one-fourth coal, the remainder being made up 

 of flour, grain, lumber, and miscellaneous freight. 



MISSISSIPPI RIVER SYSTEM. 



After the Great Lakes, the next most important system of interior 

 natural waterways is the Mississippi Eiver system. This river with 

 its tributaries affords a navigable mileage of 13,912 miles and drains 

 an area of about 1,300,000 square miles. In their original condition 

 the rivers of this system were streams of shallow depth, obstructed 

 at intervals by shoals and snags, and at certain seasons have always 

 been subject to floods of greater or less magnitude. As a means of 

 communication they were extensively used from the time that steam 

 propulsion was first applied to the shallow-draft river steamboat. 

 Before the construction of railways they were the sole means of 

 reaching many localities, but as rail construction increased their 

 commerce has been largely taken over by the rail lines in many cases. 

 The most marked movement of the country's commerce is from the 

 Avest to the east and reverse. North and south business is much less 

 in volume. It thus happens that the Mississippi River and many of 

 its tributaries do not lie along the direction of the greatest volume 

 of traffic. 



The early use of the streams depended on a successful application 

 of steam power to a light-draft boat. The flat-bottomed shallow hull 

 was thus a necessity. In order to get directive control in the swift 

 currents, enormous rudders were necessary, and so the well-known 

 gangs of three or four rudders set side by side were finally adopted ; 

 each very long, to act positively, and placed so that the preponder- 



