THE OPEN SEA 
121 
but their surfaces are always irregular, owing 
to flaws in the wind. In fact, the only line on 
the North Atlantic that has any stability about 
it is the horizon-line—the darkest line usually 
on the face of the waters. Even that is not too 
strong, owing to the presence of vaporous at- 
mosphere. It is only on cold, clear days that 
it is sharply defined. 
Wave motion is more of an appearance than 
a reality, though there is always some move- 
ment forward in each wave, and a general drift 
of the water in the direction of the blowing 
wind. That which has real movement about 
it is the undulation. This movement of the 
undulation is very apparent in the shaking 
of a carpet on the lawn or the bend and roll 
of standing grain over which the wind moves 
swiftly. Neither the carpet nor the grain 
moves forward, but the undulation certainly 
does. And it often moves at a great rate of 
speed—say fifty miles an hour—out-stripping 
sometimes the winds that set it in motion, 
just as a heavy log in a river current when 
once started will move faster than the cur- 
rent itself. One has but to watch the move- 
ment of floating objects on the waves to be 
convinced that the water itself moves but 
Undulation 
and wave 
motion, 
