THE SCHOOL OF THE SHORE 5 
Even if we keep to the shore in the nar- 
rower sense there is great variety of condi- 
tions. Take first the great masses of rock 
which often run far out to sea. Their tops and 
their seaward faces are exposed for the greater 
part of the day to the full violence of the wind 
and the heat of the sun; as the water rises the 
waves beat against them, and they are only 
completely submerged for a short time at very 
high tide. Yet even these have their inhabit- 
ants. Behind and between these weather- 
beaten masses there is shade and moisture; 
sheltered nooks and crannies abound; the 
smaller rocks at their bases are covered with 
sea-wrack, and every hollow contains a quiet 
pool of water left by the receding tide, each 
pool harbouring a crowded life. 
Beside the rocks are the great stretches of 
flat, smooth sand where we have built castles 
and dug moats, and the sands, too, have their 
own particular population, though it is not 
always easy to see it. Sometimes instead of 
sand there is shingle, gravel, or even large 
pebbles smoothed or rounded by the action of 
the waves. This kind of shore is the most 
unfavourable of all to animal life. We shall 
easily find the reason for ourselves if we bathe 
