WAVES 



277 



GLOBIGERINA. (Greatly magnified.) 



like) material of the minute shells has been dissolved in 



sinking through the deep water. No layers of this kind 



have ever been found on 



the land, and this is one of 



the reasons for believing 



that the depths of the sea 



have never been elevated 



into dry land, but that 



what is now deep ocean 



has throughout all time 



been deep ocean. 



131, Waves. Experiment 

 124. Take a long flexible 

 rubber band or tube and having 

 fastened one end, stretch it 

 somewhat. Now strike down 

 on it near one end with a small stick. A wavelike motion 

 will be seen to travel from end to end of the band. It is evident 

 that the particles of rubber do not enter into the lateral move- 

 ment, but that they simply move up and down, whereas the wave 

 movement proceeds along the band. A piece of paper folded and 

 placed lightly upon the band will move up and down but not along 

 the band. Thus wave motion does not necessitate lateral movement 

 of the particles taking part in the wave. 



When the wind blows over water, it throws the surface 

 into motion and produces waves. The highest part of the 

 wave is called the crest and the lowest part the trough. 

 Trough and crest move along rapidly over the surface of 

 the water. The particles of the water themselves, how- 

 ever, move somewhat like those in the rubber band. That 

 the water itself does not move with the wave can be seen 

 when a floating bottle is observed. It moves up and down 

 but does not move forward. If the water moved along 

 with the waves, it would be next to impossible to pro- 

 pel a boat against the direction of the wave movement. 



