DEPOSITION IN THE SEA 249 
In the partly or completely enclosed lagoons of the 
sea, where ocean waves are not violent, many forms of 
vegetation find a foothold in the sand or clay of the 
shallow water. Sediment from streams, or that brought 
by land wash or tidal currents, is filling these bays or 
Fia. 139. 
Sea-weed (the black part) covering granite rocks at Cape Ann, Mass. View 
taken at mid-tide. 
lagoons; and when the bottom has been thus raised 
nearly to the surface, various kinds of grasses take 
root and aid in building up the bottom to the level of 
the high tide, thus forming a marshy plain (Fig. 140). 
Through these salt marshes, channels extend, into 
which the rising and falling tide passes, and then, 
