150 Wisconsin Academy of Sciences^ Arts^ and Letters. 



86 feet only. The experimental improvement was made by 

 building wing-dams at suitable points along the line to be im- 

 proved. The plan adopted required only the use of brushy 

 with sufficient stone to retain the same in places and the ad- 

 dition of gravel to prevent leaks under the brush. The brush 

 was made in fascines of 11 feet long and 13 to 15 inches in di- 

 ameter, securely bound. The fascines were then formed into- 

 mats of about 9 feet wide, by placing a number of fascines side 

 by side, and placing light poles on top and bottom, and tying 

 the ends of the poles with twine. Having determined the po- 

 sition of the dam with stakes driven into the sand, a sufficient 

 number of mats were prepared as above stated, and a quantity 

 of stone and sand bags being in readiness, the work was com- 

 menced. The mates were floated into position and sunk by 

 placing stone and sand bags upon them. They were placed 

 side by side in the line of the draw, and the bottom row car- 

 ried to the entire required distance; the brush ends or tops 

 were placed up stream, and after the first course was laid the 

 tops were covered with a layer of gravel, to prevent undermin* 

 ing; and the remaining courses were carried up in the same, 

 manner ; each course was brought forward from 2 to -1 

 feet in order to break the fall of the water. After the dam 

 rose a little above low water, a substantial laver of loose brush 

 was placed along the entire face of the dam, and covered with 

 a layer of stone, and then with sufficient gravel to stop all leaks. 

 The general effect of these dams was the usual effect of con- 

 tractions ; the water was elevated above the contracted part in 

 some cases as much as six inches, but subsided again as the 

 channel accomodated itself t@ the change. In the case of cross 

 dams, a general movement of sand took place for some dist- 

 ance above, and to a considerable distance below the work ;. 

 and as soon as the current was checked there was a deposit of 

 sand in tront of the dam in its whole length. As soon as the 

 dams were brought to the surface, there was a rapid deposit of 

 sand and below the same; that above was concave, and that 



