194 



HYDRODYNAMICS. 



LEVELING INSTRUMENTS, 



The simplest mode of leveling, or ascertaining the 

 for ditches, is to cut a few yards of the ditch so 

 that water may stand in it, and then to set two sticks 

 perpendicularly, both rising to an equal height above 

 the surface. The sticks should be measured at equal 

 distances from the top downward and marked, and 



Fig. 16L 



Simple method of taking levels. 



then pressed into the earth till the water reaches the 



mark. The level may then be determmed with much 



accuracy by "sighting" over the tops of these sticks. 



Pig 162. Figure 161 exhibits this 



] arrangement. The shorter 



the sticks, and the longer 



the piece of water, the less 



will be the liability to error. 



The following simple 



mode may be sufficiently 



accurate where the descent 



of the ditch is considerable. 



A {Fig. 162) is a common 



square, placed in a slit in 



the top of the stake, B. By 



means of a plumb-hne, the 



square is brought to a level, 



when a thumb-screw at C 



fixes it fast. If the square 



Simple Leveling Instrument. 



