ALONG SHORE 
battering power of water is enormous, and it 
always works more destruction on a shallow 
coast than on adeep one. A cliff, for instance, 
that has a shelving bottom leading up to it has 
much more fury directed against it than one 
with a base seated in deep water. The waves 
will not rush forward and dash into spray 
against the latter. On the contrary, they flood 
up heavily and slowly, and seem to stop with- 
out striking a blow, the crests dancing up 
against each other rather than against the 
rocks. The reasons for this will be apparent 
if we consider for a moment the conditions 
that make possible the “breaker” and the 
“<beach-comber.” 
The surf breaks most violently over shoals or 
along a shelving beach where the bottom of the 
ocean bevels upward toward the shore. A 
wave from the sea is pushed up this incline 
with a swiftness proportionate to the propel- 
ling force behind it. The friction or drag 
upon the wave comes from the shelving bot- 
tom ; and as the shore is neared this friction is 
not only intensified by the increased abruptness 
of the incline, but also by the flow outward of 
those returning waters from the beach which 
we call the “undertow.” The result is, the 
Along the 
cliff. 
Why waves 
break. 
