IX.] WARPING 255 



ture which did not seem to add directly any food for 

 the plant. However, it is probable that with modern 

 facilities for moving earth on a large scale by steam 

 power, the improvement of much poor land might even 

 now be profitably undertaken. 



The operations which may be grouped under the 

 head of " amendments of the soil," comprise — drainage, 

 which has been dealt with elsewhere ; the marling and 

 claying of light sands ; the reclamation of peat bogs ; 

 the improvement of clay soils by liming and chalking, 

 or by paring and burning ; and lastly, the creation of 

 new alluvial soils by warping. 



Warping. 



The operation of "warping," or u colmetage," is 

 only possible in the vicinity of tidal estuaries, where 

 lands exist below the level of high water, and is in 

 this country practically confined to the estuaries of 

 the Humber and Ouse. Warping is carried out by 

 the construction of a wide drain protected by sluices 

 from the tidal river to the low land, which is first 

 divided by embankments into compartments of various 

 sizes up to 150 acres. When the embankments have 

 become consolidated, the flood tide, heavily charged 

 with suspended matter which is really fine earth 

 brought down by the river, is admitted into the 

 compartment, where it deposits most of its silt and 

 is allowed to run off when the level of the water in 

 the river has fallen during the ebb. The operation 

 is repeated until a layer of silt has formed 1 to 3 

 feet thick over the land, which is then dried and 

 brought under crop. As the chief deposit is always 

 near the mouth of the drain, where the velocity of 

 the silt-bearing current is first checked, the position 

 of the inlet must be shifted about to secure a 



