198 IRRIGATION. 



pointed and protected by a metal ring or ferule, and a 

 pointed iron pin is inserted. The implement is something 

 like a large pair of compasses with a spread of 16 1 1 2 feet 

 between the points. See fig. 85. This distance is not 

 arbitrary, but may be varied to 10, 12, or even less feet, 

 but more would be inconvenient. But 16 1 1 2 feet being 

 exactly one rod, the level may at other times answer for 

 a measurer of distances conveniently, if made of this 

 size. A spirit level is placed on the cross-bar, see fig. 86, 

 care being taken to place it exactly parallel to the line 



Fig. 86. ABRANGEMEOT OF THE SPIRIT LEVEL. 



between the bottom pins, and to verify the parallelism by 

 reversing the position of the implement as it stands upon 

 the ground upon a spot shown to be level by its first 

 position. There is no difficulty in getting the level 

 exactly placed to one who understands the use of the 

 spirit level, but unless it is placed exactly the implement 

 will be useless. To use the implement, a wooden plug is 

 driven in the ground, level with the surface, 

 at a point where the canal is to start from. One 

 of the legs of the level is placed upon the plug 

 and the other forward in the direction in which 

 the water is to flow, and from one side to an- 

 other, until a point is found which is level with 

 the starting point. A plug is then driven into 

 the ground at the second point. If the fall has 

 Fig. 87. b een fi xe( j a OIie f 00 j n 1^000 feet, which is the 

 most advisable for distributing furrows or canals, the sec- 

 ond plug should be placed a fifth of an inch below the level 

 of the first. This may easily be done with accuracy by 

 cutting off with a saw, one-half of the top of the plug 

 one-fifth of an inch below the other half, when they are 

 prepared for use. Figure 87. Then when the higher 



