DRAINAGE. 



007 



Water percolating from a river should l)e collected as near 

 it as possilile by dee^j drains running along the river-side, and 

 leading back into the river lower down stream. Overflow 

 from a stream can be kept back only by the construction of 



embankments, as in the English fen districts, or along the river 

 Severn. 



On slopes, water should be collected at the points of issue 

 from the water-bearing strata, before it can form a swamp. 

 Thus the water should be collected in a drain A- A- running 

 along a contour-line on the hill-side (Fig. 276), and then 

 conducted down-hill by a leader A along the line of greatest 



Fig. 276. 

 /•. Feeder, a. Main 

 drain at the base of ^ 

 liill. 



^^ 1 



Fig. 277. 

 D. Chief feeder. A. Main drain. 

 B. Leader from a spring q, and a 

 small swamp /. C. Feeders. 



fall, any outlying swampy places in depressions being con- 

 nected with the latter. Wherever the fall and the extent of 

 the area to be drained are considerable, several such drains 

 may be constructed, one above the other. 



