AND PROTECTION OF AGRICULTURAL LAND. 27 



Island, on the Humber, the reclamation was hastened by con- 

 structing a temporary or preliminary bank with a sluice, and 

 permitting the tidal water to flow over the land at high water, 

 when the sluice was closed, and the whole of the mud held 

 in suspension deposited, after which the sluice was raised so 

 as to allow the water to escape, leaving behind its load of 

 rich deposit. In this way he obtained in two and a half 

 years a deposit of three feet. The most rapid deposit which 

 has come under my own notice, was near the mouth of the 

 Avon, at the Severn, where the channel between Dumball 

 Island and the shore was silted up to the extent of 32 feet 

 in seven years. As a general rule, I have found that the 

 heavier sands and deposits are found on the banks at the 

 mouth of the estuary, and the particles are lighter as we recede 

 inwards. 



Such reclamation of land, however, as is due to the deposit 

 left by the free and unobstructed flow of the tide is a very 

 slow process, because in proportion as the banks rise, they 

 are more seldom covered by the tide, and, moreover, the mate- 

 rials deposited in the higher parts of the banks are exceedingly 

 fine, being carried only by the slack water of highest tides, and 

 it is not until the surface has attained a pretty high level that it 

 can be regarded as land in any agricultural sense. It has been 

 very generally found in open estuaries where the reclamation 

 is permitted to go on undisturbed by encroachments of the river, 

 that vegetation, in the form of patches of aquatic plants, begins 

 to appear when the bank has reached the level of high-water 

 mark of neap tides. As it rises above this level, its surface 

 will be found to be more or less covered with patches of 



