248 ELEMENTARY GEOLOGY 
coarsest on the headlands which are exposed to the 
action of violent waves (Fig. 138). They also vary 
in kind as well as in texture: a granite rock fur- 
nishes a different sort of pebble or sand beach from 
that which is derived from a black basaltic lava, and 
each of these differs very decidedly 
from the coral coast. The most 
striking feature of the shore line 
is coarseness of rock fragments ; 
and there are many evidences 
that nearly all the conglomerate 
and sandstone rocks on the land 
were deposited in the sea near the © 
coast line, in many cases being 
fossil beaches, now forming a part 
of the dry land. | 
Organic Deposits near the Shore. 
Diagram to illustrate varia. —~ ©2/¢ Marshes. On exposed sandy 
tion in sediment along coasts no vegetation can grow, be- 
the shore. JL, land; O, 4 
ocean; C, clay; S, sand; cause the waves continually move 
19; pebbles and Powlder the sand, and so plants would soon 
be uprooted; but where the coast 
is rock-bound, there is a covering of sea-weed from 
mid-tide to a considerable depth below the water sur- 
face (Fig 139). This serves to protect the rock from 
the attack of the waves, but it does not succeed in 
building up any distinct beds of sediment. 
Fic. 138. 
