214 SOILS 



it is supposed the drain will run; say at 5 feet. 

 The difference between the back-sight and the 

 fore-sight is thus six inches, showing that the 

 land has a fall of 6 inches in 100 feet, or in the dis- 

 tance between the two points at which the rod 

 stood. The instrument may now be moved 

 forward and similar measurements taken for the 

 remainder of the main and for the laterals. 

 The fall that the entire system can' have is thus 

 determined. 



The next thing to do is to stake out the 

 drains. Beginning at the outlet drive into the 



f round a stout peg 8 or 10 inches long until it is 

 ush with the surface. Drive similar pegs 50 

 feet apart along the line where the ditch will 

 come and about 12 inches to one side of the 

 centre of the ditch. About a foot from these 

 "grade pegs" drive "finders," stakes which project 

 a foot above the ground and guide one to the 

 grade pegs. 



The work of determining the grade and depth of 

 the ditch may now be begun, using the level as 

 indicated above and taking the height of the top of 

 each grade peg by placing the rod upon it. Thus, 

 if it has been determined that the drain may have 

 a fall of 4 inches in 100 feet, at which grade it will 

 be 3 feet 6 inches deep at the outlet, if the next 

 grade peg is four inches higher than that at the 

 outlet it shows that the bottom of the ditch at that 

 point should be 3 feet and 8 inches below the level 

 of the grade peg. Measurements are taken all 

 along the line in the same way and the depth which 

 the ditch should be at each fifty-foot point is re- 

 corded in a book, and oh each of the finder stakes. 

 When laying the tile a cord is stretched along 

 the tops of the grade stakes and the depth for laying 



