96 LAND DRAINAGE 



telescope, is the same height above the datum plane as is 

 the instrument. 



125. Cheaper levels. The instrument shown in Fig. 

 36 is rather expensive for one who has only a limited 

 amount of draining. A number of cheaper levels, also 



FIG. 37. Cheaper forms of drainage or grade levels. Reading from 

 left to right, Gurley, Jackson, Queen. 



called drainage levels, can be secured. Some of these 

 are also called grade levels. They are not as accurately 

 made as the more expensive instrument, but they are 

 sufficiently accurate for use where there is a fair fall, or 

 grade, and for others than professional drainage engineers. 

 Three such levels are shown in Fig. 37. 



