IRRIGATION 



261 



4 feet throughout the length of the pipe line. The line is so 

 constructed that the rests on top of the posts are small 

 rollers, and it is attached to the supply pipe by a turning 

 union, so that the entire pipe may be revolved and in this 

 manner the line of nozzles can be turned to the opposite 



After University of Minnesota 



Fig. 217. Irrigating garden by overhead spray 



side of the post. A line of pipe several hundred feet long 

 can be readily turned, and a number of parallel lines can be 

 connected in such a way that turning one will turn all of 

 them. The time actually required for the irrigation under 

 this system is reduced to a minimum, since the gardener can 

 open the valve and start the water, turning the pipe as 

 required in a very few minutes. It can be stopped at the 

 end of the day's work by the closing of the supply valve, or, 

 where desirable, the system can be left in operation during 

 the night. The main requisite for this method of irrigation 

 is sufficient pressure — 25 to 45 pounds — on the nozzles to 

 cause them to throw the spray the proper distance. 



