170 LAND DRAINAGE 



hose should be then manipulated as sug- 

 gested above until the air is removed, as 

 indicated by the heights of the columns 

 in checking./ 



221. Leveling rods. In determining 

 elevations with the hose-level, two rods 

 are needed, one approximately 4 feet 

 long and the other 3 feet longer, and both 

 of 1-inch X Ij-inch material. (See Figs. 

 71 and 72.) 



Observe (1) that only the long rod 

 bears a scale; (2) that both rods have a 

 zero mark at the height of 3j feet (42 

 inches) ; and (3) that the long rod has a 

 double scale one numbering down from 

 the zero mark and one numbering up 

 from the zero mark. 1 



222. Construction of rods. At pres- 

 ent, these rods cannot be bought on the 

 market and must, therefore, be home 

 made. For scales, it is convenient to 

 use yardsticks, and in the first attempts 

 made in using this method of leveling, 

 the cheap yardstick, so common for ad- 

 vertising purposes, was used. In con- 

 structing these rods, the following simple 

 directions should be observed : 



1. Have the rods straight and their 

 lower ends square ; 



1 The zero mark may be located at any 

 height, but must be at the same height on both 

 rods. 



FIG. 71. Leveling rods used with the hose-level. 

 The short rod bears the zero mark only. 



