Improvement of Land by Silting 261 



IMPROVEMENT OF LAND BY SILTING 



Nature 's method of depositing the fine silt borne 

 along by streams, whenever they overflowed their 

 banks, early suggested the idea of directing this work 

 so that the materials should be laid down on sandy 

 or gravelly soils, to so improve the texture and fer- 

 tility as to convert comparatively worthless areas into 

 extremely productive lands. 



In other cases, where marshy, low -lying lands, or 

 shallow lakes and estuaries were lying adjacent to 

 turbid streams, the waters have been so turned upon 

 them and then led away as to lay down mantles of 

 rich soil of sufficient thickness to raise the surface to 

 such a height as to permit of drainage, and thus 

 reclaim worthless swamps, converting them into rich, 

 arable fields. 



In England, where the method was introduced 

 from Italy to reclaim waste lands near the sea, the 

 process is called "warping," and in France "colmatage." 

 In England, as on the Humber, where the tides rise 

 several feet, and the waters of the river are turbid, 

 much land has been reclaimed by warping. Centuries 

 ago low, flat lands were dyked off from the sea to 

 prevent inundation; but in more recent years, to 

 this improvement was added the one under considera- 

 tion. Tide sluices, provided with gates to admit 

 the turbid water held back by the sea, were set in 

 the dykes, and the low lands were laid out in fields 

 surrounded by banks for retaining the water until 

 the sediment borne in upon the area should have time 



