316 Ground Water, Wells and Farm Drainage. 



line connecting these two stations. Of course no field will 

 be found with so regular a slope as this hut the principle 

 is no less true for being so simply stated. 



VI V IV m II 1 



_ - 6 



_ 5 



FIG. 135. Showing a system of tile drains laid out on the leveled field of 

 Pig. 133. (From Irrigation and Drainage.) 



If such a field is to be drained by placing laterals 100 

 feet apart about the maximum fall for them, and the mini- 

 mum amount of tile and ditching, will be secured by 

 placing the laterals along the lines of leveling, in which 

 case the lines I, II, III, IV, V, VI will constitute the 

 laterals on one side of the main and the lines 1, 2, 3, 4, 5, 6 

 the laterals on the other side, as represented in Fig. 135, 

 Since the lines I and 1 are both radii of the same circle and 

 have the same elevation at their outer extremities the fall 

 or gradient will be &e same or .2 of a foot per 100 feet, aa 

 shown on the contour map, but along the lines Y and 5 the 

 gradient will be .15 feet per 100 feet or 1.8 inches instead 

 of 2.4 inches per 100 feet along the lines I and 1. The fall 



