26 ON THE RECLAMATION 



tion, so that the rate at which the process of reclamation goes 

 on must depend on the quantity of matter held in suspension 

 and the shelter of the situation, so as to give sufficient dura- 

 tion of still water for its deposit. 



The amount of matter held in suspension varies, as may 

 be readily supposed, in different estuaries ; in some situations 

 it is derived from the action of the sea on a wasting line of 

 coast, in others from alluvial matter brought down by the 

 river, and in most cases, perhaps, from both of these sources 

 of supply. The size of the detrital particles carried by the 

 currents of estuaries or rivers depends on the velocity of 

 the stream, the nature of the bottom along which the detritus 

 is moved, as well as the shape of the particles of which that 

 detritus is composed, and varies with the special circumstances 

 of each locality. Observations have been made on the quan- 

 tity of solid matter held in suspension by different rivers, 

 and repeated by various authors ; but these observations have 

 invariably been made in water taken from the main stream, 

 and cannot be held to apply to such cases of reclamation as 

 we are considering, the substratum of which is slob composed 

 of the finest silt, and submerged only by sluggish currents, 

 incapable of leaving anything but the finest matter deposited 

 on its surface. It has been stated that marshes on the 

 Seine require twelve years to rise to the level of high water, 

 thirty years on the Bay of Vays, and eighty years on the 

 Scheldt, and similar variations are to be found in statements 

 made by various authors. Mr Oldham * states that at Sunk 



* On Reclaiming Land. By James Oldham, Min. of Proc. of Inst. of Civil 

 Engineers, vol. xxi. 



