TILE DRAINAGE 31 



been found to be one foot in 100 or .5 of a foot in 50. If 

 the ditch was to be dug to the same level at the first stake 

 as at the outlet, the depth would be found by subtracting 

 the reading, 4.4 feet, from 8.3 feet. But since the fall of 

 the drain is to be .5 feet from the first stake to the outlet, 

 the depth will be .5 feet less than the difference between 

 8.3 and 4.4. From the second stake to the outlet the fall is 

 to be one foot, so the depth of the ditch will be one foot 

 less than the difference between the reading, 3.7 feet, and 

 8.3 feet, which gives 3.6 feet. In the same manner the 

 depth at each stake is found by taking the sum of the 

 reading and the faU to the outlet from the height of the 

 instrument above the level of the outlet. After the depth 

 to which the ditch is to be dug at the various stakes has 

 been determined, it is plainly marked on each stake for the 

 guidance of the digger. 



DIGGING THE DITCH. 



When the stakes are first set they should be placed m 

 line so that the ditch will be straight. The digging should 

 begin at the outlet and a line should be •stretched from 

 one stake to the next to aid in marking out the ditch. It 

 is best to dig the ditch about six inches to one side of the 

 line of stakes, so that there will be no danger of them 

 being broken off or caving into the ditch. A plow can 

 sometimes be used to advantage in opening the ditch, but 

 care must be taken that the grade stakes are not dis- 

 turbed. In Figure 5 are shown some of the hand tools used 

 for making drainage ditches. No. 1 is the common short- 

 handled shovel, which can be used to throw out a consid- 

 erable part of the dirt and sometimes all of it. No. 2 has 

 a handle six feet long and is used for grooving the bot- 

 tom of the ditch for round tile. No. 3 is a heavy spade 

 for use in soft ground. No. 4 is a long-handled tool for 

 grooving the bottom for six-sided tile. No. 5 is a bot- 

 toming spade for digging near the bottom of the ditch 

 where a narrow width is wanted. No. 6 is a flat spade 



