AMELIORATION OF LAND 81 



drainage, it means that the working expenses 

 generally are reduced, and if to such reduc- 

 tion is added a considerable increase in the 

 yield, a large net return may remain over 

 after meeting the cost of drainage. 



Depending on the cause of wetness, land 

 may be freed of its surplus water by methods 

 of prevention or of cure. It may be possible 

 to hinder water getting on to land, as is the 

 case where rivers are provided with embank- 

 ments to prevent overflow during periods of 

 flood. Then, again, land that is subject to 

 inundation, owing to the slow current of 

 an adjoining stream, will be rendered less 

 liable to submersion if the course of the 

 brook or stream is straightened, so that 

 flood water may flow away more quickly. 

 This result is due partly to the reduction of 

 friction between the water and the bottom 

 and sides of the stream, and partly to the 

 fact that a straight course is necessarily 

 the shortest course between any two points, 

 and thus the fall of the water is relatively 

 increased. If, for example, the distance 

 between two points, A and B, on a winding 

 stream is 800 yards, and the difference in 

 level is 6 feet, the fall is 1 in 400. Should 

 a straight channel be cut between the two 

 points, the distance that the water has to 



