CANAL CONSTRUCTION. 6 1 



thick. Beginning at the highest point on the land to 

 which the water is to be condu(5led, drive a stake so that 

 its top will be six inches above the surface of the earth. 

 On the top of this stake place the end of the straight- 

 edge to which the quarter-inch block is fastened, the 

 block resting on the stake. Drive the next stake one rod 

 from the first stake, toward the source of the stream, 

 at such a point that the second stake is driven so as to 

 project six inches above the surface of the earth. 

 With the straight-edge resting on both stakes the 

 spirit will thus indicate a true level. Obviously a 

 ditch dug between these two stakes, at a uniform 

 depth below the top of each stake, will be one- fourth 

 of an inch deeper at the lower end. Proceed thus until 

 the top of the last stake is six inches above the surface 

 of the water in the stream. Be careful not to reverse 

 ends of the straight-edge level, but keep the end to 

 which the block is fastened down-stream. The line 

 indicated by the stakes is the ditch line, and the bot- 

 tom of the ditch should be at a uniform distance below 

 the top of each stake. These instru<5lions are only 

 available in small work, such as an ordinary farmer 

 might require in an individual way, and cannot apply 

 to the work of excavating a great canal, which should 

 be surveyed in the scientific manner. 



Ditching Methods. — With regard to excavation 

 and costs, the smaller ditches may be construdled by 

 hand shoveling, by plowing, and by scraping, or by 

 plowing with a large double-mold-board plow ; the 

 larger ditches by plowing and scraping, or by grading 

 or ditching machines. Hand-work is of course most 

 expensive, but it will be necessary in some places. 



