260 ENGINEERING ON THE FARM 



near the surface, which prevents the escape of the water 

 downward, good results are secured. It is necessary that 

 clean water be used, as sediment carried in the water will 

 be deposited in the pipes when the water is taken up by the 

 soil. In a few localities drain tile has been laid in such a 

 way that during the wet season it serves for drainage pur- 

 poses and during the dry season the outlet is cut off and 

 the water supply is delivered through the tile, which then 

 serves as a subsurface irrigation system. However, it is 

 only occasionally that this combination will work to any 

 advantage. 



Spray irrigation. The spray method is a system which has 

 been developed from the sprinkler in its use on lawns, and 

 is the popular method for irrigation in the East, where it is 

 much more extensively used than in the West. It is appli- 

 cable to small areas and small water supply and does not 

 require any special preparation of the surface. Further- 

 more, the application of the water requires very little 

 attention. The first cost of the system is comparatively 

 large, but in the estimation of gardeners and small fruit 

 growers its merits from all other standpoints outweigh the 

 initial cost. 



Hose with movable nozzles fed from underground pipes 

 or circular nozzles directly connected with the pipes are used. 

 This system is applicable in greenhouses, cold frames, hot 

 beds, or field irrigation. The method of overhead spray 

 lines fed from an underground main is the one most favored 

 at the present time (Fig. 217). The water is piped to the 

 points of distribution in the field and distributed by means 

 of pipes supported on posts, the pipes being of sufficient 

 height to allow a team to pass under them. These pipes 

 decrease in size from the supply pipe to the outer end, so 

 that the quantity of water delivered and the pressure are 

 constant throughout the pipe. To distribute the water 

 properly and to throw a spray as great a distance as prac- 

 ticable, small brass nozzles are inserted approximately every 



