DKVICKS, APPI.IANCKS AND CONTRIVANCES. 407 



end thrust to a good depth in the earth at the bottom 

 of the ditch. 



The author has used — many years ago, however — a 

 metalHc dam consisting of a sheet of galvanized iron, 

 about thirty inches long and fifteen inches wide, and 

 having two rounded corners. There was an aperture 

 four by ten inches square in the center for the water to 

 flow through. When the gate was in position the flow 

 of water through the aperture was regulated by a 

 sliding adjustable 

 gate, made also of 

 galvanized iron, 

 easily moved up or 

 down by hand. 

 The dam was set 

 in position across a 

 lateral by crowd- 

 ing its sharp edges 

 down into the soil 

 to the proper depth, 

 thus forming a 

 check to the flow of the water in the lateral except as 

 it passed through the sliding gate. 



The Witcher dam is a patented improvement over 

 the apron and diaper sheets. It is composed of a large 

 piece of canvas secured on one edge to a beam or pole 

 which spans the ditch. The side edges are laid on the 

 banks, while the lower edge lies across the bottom of 

 the ditch or canal. The front is adjustably looped by a 

 rope in the middle, regulating the water to a predeter- 

 mined stage, and causing it to pass through the branch 

 ditch or canal. The main pressure is supported by 



FIG. 97 — HUNTLEY DAM. 



