410 CHARACTER OF GROUNDS DIKED IN. 
of the rivers which contribute it, according to the varying drift 
of the currents. . 
Marine Deposits. 
The process of natural deposit which prepares the coast for 
diking-in is thus described by Staring: “ All sea-deposited soil 
is composed of the same constituents. First comes a stratuin 
of sand, with marine shells, or the shells of mollusks living in 
brackish water. If there be tides, and, of course, flowing and 
ebbing currents, mud is let fall upon the sand only after the 
latter has been raised above low-water mark; for then only, at 
the change from flood to ebb, is the water still enough to form 
a deposit of so light a material. Where mud is found at great 
depths, as, for example, in a large proportion of the Jj, it is a 
proof that at this point there was never any considerable tidal 
flow or other current. . . . The powerful tidal currents, 
flowing and ebbing twice a day, drift sand with them. They 
scoop out the bottom at one point, raise it at another, and the 
sand-banks in the current are continually shifting. As soon as 
a bank raises itself above low-water mark, flags and reeds es- 
tablish themselves upon it. The mechanical resistance of these 
plants checks the retreat of the high water and favors the 
deposit of the earth suspended in it, and the formation of land 
goes on with surprising rapidity. When it has risen to high- 
water level, it is soon covered with grasses, and becomes what 
is called schor in Zeeland, kwelder in Friesland. Such grounds 
are the foundation or starting-point of the process of diking. 
When they are once elevated to the flood-tide level, no more 
mud is deposited upon them except by extraordinary high tides. 
Their further rise is, accordingly, very slow, and it is seldom 
advantageous to delay longer the operation of diking.” * 
* Voormaals en Thans, pp. 150,151. According to Reventloy, conferve 
first appear at the bottom in shoal water, then, after the deposit has risen 
above the surface, Sulicornia herbacea, The Salicornia is followed by various 
sand-plants, and so the ground rises, by Poa distans and Poa maritum, and 
finally common grasses establish themselves. —Om Markdannelsen poa Vesthys- 
ten af Slesvig, pp. 7, 8. 
