182 



THE IRRIGATION AGE. 



The cloth dam (Fig. 9) is very widely used. It consists of a rect- 

 angular piece of stout, closely-woven cloth or canvas, one side of 

 which is rolled around and nailed to a crosspiece of wood of length 

 and strength according to the size of the ditch and the amount of 

 water to be dammed. Sometimes it is made with a hem across one 

 side deep enough to allow the crosspiece to be thrust through the 

 hem, In using the dam, place the stick across the top of the dry 

 ditch where it is desired to throw the water out; draw the lower edge 

 of the cloth up the bottom of the ditch and place a little dirt on the 

 corners. (Sec Fig. 12) 

 The canvas must al- 

 ways be large enough 

 to have several inches 

 lap against the sides 

 of the ditch; otherwise 

 it will not retain all the 

 water. Should the 

 ditch have a steep 

 grade it will be neces- 

 sary to let the canvas Fig 9 TheClcth Dam . 

 fill up gradually, as a sudden rush of water would force the cloth 

 from its position, When the dam is in position it will be necessary to 

 cut the bank of the ditch at the places where the water is wanted. 

 Two cloth dams will be needed in order to place one in position while 



the other throws the water out 

 above, it being difficult to lay 

 the canvas under a full head of 

 water. The water will press the 

 canvas against- the sides and bot- 

 tom of the ditch, so that none can 

 escape. To remove the cloth, 

 take hold of one end of the scant- 

 ling and pull slowly up stream. 



Fig. 10. The Metal Dam or Tappoon. 



A metal dam or "tappoon" is on some accounts preferable to the 

 cloth, and it, too, is readily made. Heavy sheet iron is cut into semi- 

 circular shape and the straight edge is securely fastened between two 

 narrow strips of wood by carriage bolts which pass through the strips 

 and through holes punched in the iron sheet (Fig. 10), or it may be 

 more cheaply made by securely nailing the iron to one side of a single 

 thicker strip of wood, like a piece of scantling. These metal dams 

 are made of different sizes according to the ditch in which they are 

 to be used, their diameter being a little more than the width of the 

 ditch, as the edges must be pushed down a little way into the earth of 



