LEVELING LOCATION 
399 
In staking out founclation-pits, set temporary stakes exactly 
above the intended bottom angles of the completed pit, thus mark 
ing out on the surface of the 
ground its intended shape. 
Take the heights of each of 
these stakes and move them 
outward such distances that 
cutting down from them 
with the proper depth and 
slope will bring you to the 
desired bottom angle. 
568. To locate a Level-Line. This consists in determining on 
the surface of the ground a series of points which are at the same 
level—i. e., at the same height above some datum. Set one peg at 
the desired height, as in Art. 565. Sight to the rod held thereon, 
and make fast the target when bisected. Then send on the rod in 
the desired direction, and have it moved up or down along the slope 
of the ground, until the target is again bisected. This gives a sec 
ond point. So go on as far as sights can be correctly taken, keeping 
unchanged the instrument and target. Make the last point sighted 
to a (l ‘ turning-point.” Carry the instrument beyond it, set up 
again, take a B. S., and proceed as at first. 
The rod should be held and pegs driven at points so near to 
gether that the level-line between them will be approximately 
straight. 
Fig. 408. 
569. Applications. One use of this operation is to mark out 
the line which will be the edge of the w T ater of a pond to be formed 
by a dam. In that case, a point of a height equal to that of the 
top of the proposed dam, plus the height which the water will 
stand on it (to be determined by hydraulic formulas), will be the 
starting-point. Then proceed to set stakes as directed in the last 
article. 
The line from stake to stake may then be surveyed like the 
sides of a field, and the area to be overflowed thus determined. 
Strictly, the surface of the water behind a dam is not level,