FLOW OF WATER THROUGH PIPES. I3I 



should be to remove the surface water quite quickly and 

 secure a gradual movement of sub-surface water through 

 the soil into the drains. The action of the water in 

 passing slowly through the soil is beneficial in imparting 

 to it such fertilizing gases as it may have absorbed from 

 the atmosphere, and in disintegrating soil particles and 

 helping to prepare them for plant food. With this ob- 

 ject in view, sufficient drainage is better than too much. 



The rainfall is exceedingly variable both with respect 

 to the season of precipitation and the quantity which 

 falls, so that a system of drains which would prove 

 ample during one year, or even for a series of years, 

 would at other times become overcharged and prove 

 insufficient for the work desired. 



The land to be drained is in some localities a level 

 tract, in others it is broken up by ridges, slopes, ponds, 

 and swamps alternating in irregular variety, thereby 

 greatly complicating the plans which must be used for 

 draining successfully as well as the determination of the 

 size of the drains for the same. 



The drains ordinarily used for the work are not uni- 

 form either in the quality of the material or excellence 

 of the workmanship when constructed. The drain re- 

 ceives water at all of the joints, and in the case of mains 

 at various points where branches join . These discharge 

 into the main under varying heads and grades. 



It follows that it is no easy matter to formulate the 

 elements which enter into economical and efficient land 

 drainage so as to put the subject of the flow of water in 

 drains on a scientific and at the same time a practical 

 basis. 



It has been found, however, by observations and 



