On the Wisconsin River Improvement. 149 



the current. During a continuous stage of water, the move- 

 ment is slow and regular, and the bars are moved along as an 

 obstruction by the pressure rather than by the velocity of the 

 water, rolling slowly and steadily along the bottom with no 

 floating sand, until the equilibrium is disturbed. When 

 moved by the velocity of the water, they move quite rapidly, 

 and the sand is found floating in the water in quantities. He 

 gives an instance of a bar above Steamboat Slough, contain- 

 ing a uniform depth of water of twenty-two inches at a cer- 

 tain stage of water. After the water had fallen twelve inches, 

 the same amount was found ; also subsequently when the river 

 had risen again a little above its former stage, still the same 

 amount of water covered the bar, clearly indicating the exist- 

 ence of equilibrium between the current and weight of sand. 

 In order to determine the most favorable condition of equi- 

 librium to preserve a good channel, a section was measured 

 near Lone Rock, where the channel is quite uniform for sev- 

 eral hundred feet, and the stream at low water is confined to 

 one channel of 325 feet between banks ; the greatest depth 

 was 7.4 feet, and the mean depth six feet, giving the cross- 

 section of 1,950 square feet ; a series of floats gave a mean ve- 

 locity of 1.95 miles per hour; the channel in question always 

 preserves a uniform depth, and is free from sand-bars. As 

 there are many similar places on the river, it will be safe to 

 assume from these the necessary section for any required 

 depth of water. 



Aside from the sand bars, the only other obstruction to nav- 

 igation are the railroad bridges an J the principal difficulty with 

 these is that they are built obliquely across the stream ; the 

 water is thereby inclined to flow to the bank at the down- 

 stream end ; whereas the draws of both the Spring Green and 

 Lone Rock bridges are at the opposite or up-stream end ; in 

 addition to this the draw spans are very narrow; and still more 

 contracted by the piles and protection of the pier-loun- 

 dations, making the entire available width at low water about 



