Location of Drains. 



315 



Table giving data obtained in leveling field of Fig. 1SS. 



388. Contour Map of Field, When the field has been laid 

 out as represented in Fig. 133, and the elevations of the 

 several stations transferred to the map, the figures show at 



FIG. 134. Showing method of leveling. 



a glance where the field i: high and where it is low. If 

 now lines are drawn upon the map through all places hav- 

 ing the same elevation the topography of the field becomes 

 still more evident to the eye. Such lines are called con- 

 tours or contour lines, and such are the dotted lines in the 

 map. 



389. Location of Mains and Laterals. It is clear from the 

 contour map that the highest station in the field is VI 6 

 and the lowest 1-1. If then we are seeking the steepeet fall 

 or gradient for the main it will be found along a straight 



