552 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1916. 



ance of the length aft of the rudder post was slight, in order to 

 reduce the power necessary to move them. The propelling power 

 had to be applied in such a way as to give quick strong action in 

 flood currents and enable the rudders to act while backing. This 

 required a powerful stern wheel. The type of boat evolved under 

 these conditions has not changed much in recent years and its 

 efficiency has not been increased equally with rail power. The Gov- 

 ernment, however, has endeavored to examine into this question and an 

 appropriation of $500,000 was made in 1910 to make experiments with 

 a view to reducing the expense of river towmg on the Mississippi and 

 its tributaries. Several experimental boats have been tried and are 

 now being tested. Such favorable results have been met with in the 

 twin screw " tunnel " type of steamboat that two are now being built 

 for the lower Mississippi. Twin screws working in longitudinal 

 tubes, or " tunnels," under and within the hull are the propelling 

 power. 



The Mississippi Kiver is separated into three distinct parts — that 

 above the mouth of the Ohio River, that between the Ohio and Mis- 

 souri Rivers, and that below the mouth of the Missouri. In these 

 parts the differences in the character of the river and in the methods 

 of channel construction are conspicuous. From St. Paul to St. Louis, 

 658 miles, the river was originally obstructed in many places by rock 

 rapids and sand shoals. The first plan for its deepening was adopted 

 in 1879 and provided for a channel depth of 4| feet over the whole 

 distance. This was to be obtained by open river regulation. Here 

 is to be found the most perfect instance of this class of river work 

 in this country and is excelled in effectiveness nowhere. For many 

 years the projected depth has been maintained throughout. The 

 work has cost a little over $12,000,000. In 1907 it was proposed to 

 increase the channel depth to 6 feet throughout the length of this 

 part of the river, at an estimated cost of $20,000,000, with a view to 

 its completion within 12 years. This project was adopted and work 

 has been under way since then. The work is now about one-fourth 

 done. 



The available water power of the river attracted capital a few years 

 ago, and the large market near at hand for electric power and the 

 amount of water power going to waste induced engineers to propose 

 a commercial enterprise which would save this waste and assist, 

 incidentally, in the navigation of the river. Accordingly, at Keokuk, 

 Iowa, a power dam has recently been built by private funds, which 

 raises the water surface 40 feet. This has covered the former Gov- 

 ernment canal around the rapids at Des Moines. It has backed the 

 river up about 60 miles, affording 6-foot navigation for this distance. 

 It is provided with locks for passing vessels. This work is a fine 

 example of an industry that is increasing rapidly in importance in 



