14 The Sea 
all the way around the Cape of Good Hope to the English 
Channel—a distance of more than 14,000 miles! Before the 
explosion the island possessed a mountain peak 2600 feet 
high; after the disaster the island was leveled to the sea; in- 
deed much of the violence of the explosion is supposed to 
have been due to the flowing of the sea into the incandescent 
crater of the volcano. For years after the explosion the dust 
from it remained in the upper air, causing gorgeous red sun- | 
sets all around the world. 
CALMS AND RIPPLES 
There is scarcely a day when the water is so calm that 
there are not some waves visible. The lightest breath of air 
gives rise to small waves called ripples. The physical mecha- 
nism of the smallest waves is somewhat different from that of 
the larger ocean waves inasmuch as it is mostly controlled by 
the surface tension of the topmost layer of water. Their shape 
is unlike their bigger brothers. They have a so-called sinu- 
soidal shape instead of a trochoidal one. (See illustration on 
page 5.) Ripples are produced by the wind. They give 
warning of a squall or gust of wind. The sailor is warned of a 
squall while it is still a good distance off by the appearance 
of a confusion of ripples moving rapidly toward him. 
WATER VIBRATIONS 
Almost all objects may be made to vibrate. When you 
strike a bell or pluck a stringed instrument you get a particu- — 
lar sound. The pitch and other characteristics of the sound ; 
produced depend upon the way the bell or string vibrates 
when struck. Because different objects have certain preferred ~ 
ways of vibrating we can obtain definite tones. As a matter — 
of fact all things have certain preferred ways of vibrating. It ; 
