106 LAND DRAINAGE 



and, by the use of wide thin wedges, adjusted to level. 

 Over the top of the level thus adjusted the operator may 

 sight. Figure 41 shows the level in use. 



144. The water level. Figure 42 shows what is some- 

 times spoken of as the water level. It consists, in this 

 case, of two glass tubes firmly clamped to a bar which in 

 turn is firmly fastened to a sharpened leg. The lower 



FIG. 42. Illustrating the water level in use. 



ends of the tubes are connected by a piece of rubber tub- 

 ing. A colored fluid is introduced through one of the 

 tubes until it stands within an inch of the tops of the 

 glass tubes, care being taken to have the bar nearly 

 horizontal. In accordance with a law of fluids, the tops 

 of the columns of colored liquid in the glass tubes stand 

 at the same level. A line passing over the tops of the 

 columns of fluid, therefore, when the fluid has come to 

 rest, is level. Sometimes horizontal sliding sights are 

 set on the tubes. When the fluid comes to rest, each sight 

 is set even with the top of the column of fluid in its tube. 

 The sighting is then done over these sights. (See also 

 Fig. 43.) 



With these home-made devices there must also be used 

 a leveling rod, which is also usually home-made, the 

 making of which will vary with the notions of the maker. 



