EXTENSIOlSr COURSE IN SOILS. 37 



level of the bottom of the ditch between the stakes which are 50 feet 

 apart. 



The height of the bottom of the ditch or the grade line, above the 

 outlet can now be determined for each grade stake. These heights 

 should be written in a column opposite the elevations of the surface 

 of the ground. By subtracting the elevation of the grade line from 

 that of the surface of the ground, the depth of cut can be found at 

 each stake. These depths can be written in proper order in a third 

 column. 



The construction of the ditch may now be undertaken. (Ref . No. 

 8, pp. 89-98.) This should be started at the lower end, or outlet. 

 It is necessary now to have a method of determining exactly when 

 the grade Hne or bottom of the ditch is reached. To do this, place 

 strong stakes at each of the two lower stakes with a line between. 

 This hne is to be placed at a uniform height above the bottom of 

 the finished ditch. A string may be adjusted at a convenient height 

 of 5 or 6 feet above the bottom of the ditch by subtracting the depth 

 of digging at each stake from the 5 or 6 feet decided on and measuring 

 up from the surface of the ground this distance on the stake. Fas- 

 tening the string at this point for each of the two stakes will bring 

 the string exactly parallel with the bottom of the ditch and 5 or 6 feet 

 above it. 



Digging the ditch and completing the drain. — The tools necessary 

 include a ditching spade with a blade about 8 inches wide, slightly 

 curved, and square at the cutting edge; a long-handled pointed 

 shovel; a tile scoop; and, if much tile is to be laid, a tile hook. A 

 strong string is first stretched along the edge of the ditch to keep it 

 straight. Digging begins at the lower end and proceeds upgrade 

 in sections, removing the dirt to a spade depth at a time. The 

 width of the ditch will depend on the depth but should be no greater 

 than is absolutely necessary. Care must be taken not to remove 

 dirt below the grade Hne. When the grade Hne is nearly reached 

 over a distance of 6 or 8 feet the last thin layer of dirt is removed 

 with the tile scoop, which produces a straight, smooth bottom on 

 which the tile may be placed. Tile may be placed by hand, though 

 if the ditch is deep and much is to be laid the tile hook will permit 

 much more rapid and easy work. The tile should be placed so that 

 they fit closely together end to end, and care must be taken whenever 

 work is left for the night to have the upper end protected by a flat 

 stone or otherwise so that much soil may not be washed in in case of 

 rain. The tile should be covered immediately after laying to a depth 

 of 2 or 3 inches after heavy soil or other material has been used over 

 joints to prevent sand or other loose material from working into the 

 tile. (Ref. No. 8, p. 99.) This is called blinding. The remainder 



