Action of Waves. 375 
‘mare’s-tails lying about; for their stems are hollow, 
and have knots at regular intervals. 
After a continuance of the wind in one quarter for 
a few days—south or south-west—the opposite shores 
are lined with such weeds carried across, together with 
great quantities of dead branches fallen from the trees 
and willows. So that onasmall scale the same thing 
happens as with the drift wood of the ocean; and, 
indeed, by studying the action of natural forces as 
exhibited in our own pools and brooks, it becomes 
much easier to comprehend the gigantic operations 
by which the surface of the earth is altered. 
For instance, the north-eastern edge of the water 
is continually encroaching on the land, eating away 
the sandy soil, showing that the prevalent winds are 
south and west. The waves, thrown against the shore 
with the force they have acquired in rolling six or 
seven hundred yards, wash away the earth and un- 
dermine the bank, forming a miniature cliff or preci- 
pice, the face of which is always concave, projecting 
a little at the foot and also at the top. So much is 
this the case that an unwary person walking too near 
the edge may feel the sward suddenly yield and find 
it necessary to scramble off before a few hundred- 
weights of earth subside into the water. 
In this process the loamy part of the earth is 
dissipated, or rather held in suspension, while the small 
stones and ultimately the heavier sand fall to the 
bottom and form the sandy floor preferred by the fish. 
