SUBIRRIGATION AND SUBSOILING. 427 



escape in considerable part through the openings along 

 the side. For this reason the pipes should be laid very 

 nearly level, but if a considerable slope cannot be 

 avoided it has been found best to have cut-offs in the 

 pipe every ten or twenty feet to check the flow. 



Another way is to run the main pipe on the down 

 grade and connedl this with irrigating pipes branching 

 from it with suitable valves or cut-offs, so that the 

 water can be turned into the branches. The pre- 

 ferred length of irrigating pipe is about 200 feet. 

 Sometimes double T's are provided on the main supply 

 pipe to connedl with the pipes on each side. The 

 main vSUpply pipe is proportioned according to the 

 amount of water to be carried. In general, for garden 

 and orchards it is one and one- fourth inches in 

 diameter. One style of sheet-iron lateral pipe has an 

 open seam along its length, and is usually seven-eighths 

 of an inch in diameter, although smaller sizes can be 

 used for flower beds. The cost varies according to the 

 amount used, but in one case where three acres were 

 provided, two of these in orchard and the remaining 

 acre devoted to potatoes, watermelons, and other 

 vegetables, the entire cost was $63. In this case the 

 watermelons alone paid the cost of the pipe. One man 

 can lay 3,000 feet in a day by covering with a plow. 



In order to subirrigate a trac5l with a windmill, one 

 should have a reservoir or tank that will hold at least 

 800 or 1,000 barrels, and unless one is reasonably sure 

 of sufficient wind to fill the tank within three days 

 at all times throughout the summer, a corresponding 

 increase would be necessary. A reservoir that will 

 hold 3,000 or 4,000 barrels would, in many places, be 



