314: Ground Water, Wells and Farm Drainage. 



and is placed in the column headed "difference." The first 

 difference added to the datum, 10, gives 10.2, the hight 

 of station 1-2 above the datum plane. The second differ- 

 VI V IV III II I 



FIG. 133. Sliowiug method of leveling a field. 



ence, .2, added to the elevation of station 1-2 gives 10.4, 

 the elevation of station 1-3 above datum. In this manner 

 the level is moved from station to station until e is reached 

 when it is transferred to f and back sights and fore sights 

 taken as before, and entered in the table to connect the 

 first line of observations with the new one jv.st begun. 



Proceeding as before the level is moved from f to g and 

 then through h, i, j, k and 1 to m and so on until the field 

 is all completed. When proceeding from higher to lower 

 levels the differences must be subtracted rather than added 

 to obtain the elevation of the lower station. Fig. 134 shows 

 the relation of the level to the target rod along a single 

 line of stations shown in profile. 



