184 



LAND DRAINAGE 



inches and 1-^ eighths below the level mark, and so on 

 down to stake 1. 



TABLE XXI 



241. Placing the marks for grade bars. A permanent 

 mark (with pencil, chisel, or knife) should be made on the 

 inner edge of each stake to indicate the proper height of 

 grade bar. And this height is obtained for any stake by 

 carefully measuring down from the datum plane on that 

 stake, with a rule or yardstick, the distance indicated 

 for that stake in column 4 of the table. 



242. Checking up on depth of ditch. Before putting 

 up the grade bars, it will be well to check up on the depths 

 of the ditch at a few points along the line, and, if the ground 

 is rather irregular, at all points. It may be that a con- 

 stant grade, or fall, from stake 9 to stake 1 may call for 

 too great a depth of ditch at some point, or too shallow 

 a depth at some other. The bottom of the finished ditch 

 stands 5 feet 6 inches below the boning line. With a 

 rule or yardstick, determine the distance at stake 2 from 



