26o 



Bulletin 254. 



there is a large body of land in the 

 same neighborhood to be drained, it 

 is advisable that a drainage level 

 similar to the one shown in Fig. 196 

 be employed on all doubtful proposi- 

 tions. This level costs about $30,00 

 and the leveling rod shown 

 in Fig. 197 costs $10.00 and 

 these may be purchased by 

 one man or by several men 

 acting in co-operation. A 

 drainage system is such a 

 permanent investment and 

 involves so large an amount 

 of money that no reason- 

 able precautions should 

 be neglected to insure 

 its perfect working. Full 

 directions for the use of 

 such an instrument may be 

 found in books on civil 

 engineering and particularly 

 on land drainage and direc- 



Fia 196.— .4 tyi^e of level that tions for the manipulating of 

 may be used in laying out farm ., . ^ ^ ,. . 



drainage systems. the mstruments are supplied 



by the manufacturers. 

 But in a large number of propositions the fall is so 

 apparent and the outlet so clearly defined and adequate 

 that no leveling instruments of any sort are necessary. 

 In all such cases the general course of the mains and 

 laterals should be staked out in advance of any excavation, 

 beginning at the oudet. If the ditch is to be in a natural target ~od 

 depression in which water is likely to flow over tlie -^'"^"^'/t' for 

 surface even after the installation of the tile, the tile level shown 

 should be placed a little to one side of the bottom of the ^"" ft git re 

 depression to prevent any possibility of its being washed 

 out. Wherever a lateral joins a main drain or for that matter 

 wherever two drains unite, they should come together at an acute 

 angle instead of at a right angle, with the flow of the water di- 

 rected with the fall. This arrangement reduces the tendency to 

 check the flow of water in the tile, thereby causing the deposition 

 of material in suspension which might clog the tile. This arrange- 



