no IRRIGATION FARMING. 



little attention, whereas ditches, however well they 

 may be made, will require an annual overhauling. The 

 advantage over a flume lies in the fadl that evaporation 

 and leakage are done away with. It is here assumed 

 that a pipe connedls with a well or fountainhead, as 

 otherwise there could be no pressure upon the pipe and 

 it would vStand in relation to delivery on a plane with 

 the ditch or flume. If the line is accommodated to the 

 surface and there is any inverted or downward bend in 

 the pipe, there should be a valve set at the lowest 

 point to provide for the emptying or draining of the 

 pipe during cold weather, or for repairs. The pipe 

 may be laid on or near the surface on low supports of 

 such form and material as circumstances may suggest. 

 The matter of grade is of little importance, for the 

 water being forced will run up hill as well as down, 

 and a pipe may be laid to the natural grade of the sur- 

 face and deliver water on a level with the fountain- 

 head. 



Pressure of Pipes. — For the purpose of consider- 

 ing the pressure we will divide the classes of pipes 

 into three kinds : low-pressure pipes, medium-pres- 

 sure pipes and high-pressure pipes. By low-pressure 

 pipes we mean those which are not required to with- 

 stand any greater pressure than that occasioned by the 

 gravity flow of water through them, with the addition 

 of a few feet if necessary. We will designate as 

 medium-pressure pipes those which are able to with- 

 stand a pressure of fifty pounds to the square inch with 

 safety, and as high-pressure pipes those which can 

 safely resist a pressure of 120 pounds to the square 

 inch. Pipes made of riveted sheet iron or steel No. 16, 



