200 ENGINEERING FOR LAND DRAINAGE. 



taking into account the drainage advantages which each 

 property possesses by nature. 



The work should be undertaken only after it has been 

 shown that the benefits which will accrue to the prop- 

 erties concerned will be greater than the expense of 

 the improvement, and should be executed with due 

 regard to economy and permanency. 



Plans, 



The natural boundary of the area should be deter- 

 mined with accuracy. Where the drainage divide is 

 not apparent from observation, levels should be taken 

 to determine the dividing line between water-sheds, for 

 upon this point will often depend the legality of assess- 

 ments upon certain tracts for the cost. There are table- 

 lands or levels where there is no little difficulty in 

 determining the natural divide. In fact some tracts 

 may be drained by artificial methods as easily in one 

 direction as in another, but the natural drainage of a 

 tract as held by the courts is the direction in which 

 the water will flow when the entire surface of the land 

 becomes covered with water. The belt of land which 

 first becomes dry when drainage takes place under 

 such conditions is the natural divide, and should be 

 regarded as the boundary line of the area to be in- 

 cluded in a district. A map should be made showing 

 the acreage and ownership of each farm, and upon this 

 the boundary line of the district should be distinctly 

 marked. The natural outlet for the district may be 

 obvious, but its size insufficient, in which case it should 

 be improved. The size and best dimensions for the 



