THE SILURIAN BEACH. 45 
it greater force at that point, so that the sand 
around the spot is soaked and loosened. There 
is still another sign, equally familiar to those who 
have watched the action of water on a beach. 
Where a shore is very shelving and flat, so that 
the waves do not recede in ripples from it, but in 
one unbroken sheet, the sand and small pebbles 
aie dragged and iorm lines which diverge when- 
e\ei the water meets an obstacle, thus forming 
sharp angles on the sand. Such marks are as 
distinct on the oldest Silurian rocks as if they 
had been made yesterday. Nor are these the 
on ly indications ol the same fact. There are cer 
tain animals living always upon sandy or muddy 
shores, which require for their well-being that 
the beach should be left dry a part of the day. 
These animals, moving about in the sand or mud 
from which the water has retreated, leave their 
tracks there ; and if, at such a time, the wind is 
blowing dust over the beach, and the sun is hot 
enough to bake it upon the impressions so formed, 
they are left in a kind of mould. Such trails and 
furrows, made by small Shells or Crustacea, are 
also found in plenty on the oldest deposits. 
Admitting it, then, to be a beach, let us begin 
with the lowest type of the Animal Kingdom, 
and see what Kadiates are to be found there. 
There are plenty of Corals, but they are not the 
same kinds of Corals as those that build up our 
