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FIEST YEAR SCIENCE 



That it is possible to generate wave movement with- 

 out the particles themselves moving along with the wave 

 is seen when a field of grain is bending before a gentle 

 wind. The troughs and crests move one after the other 

 across the field but the heads of grain simply vibrate back 

 and forth. The crest of a water wave, however, is often 

 blown forward by the wind and thus a drift in the direc- 

 tion of the wind is established at the surface. 



OCEAN WAVES. 



When great waves are raised by the wind at sea, there 

 is danger that the mighty crests may be blown forward 

 and engulf a ship. To calm the waves ships sometimes 

 pour "oil on the troubled waters." The oil spreads 

 out in a thin film over the water and forms a " slick " 

 which prevents the wind from getting sufficient hold upon 

 the water to topple over the crests, and thus the danger 

 of being swamped is averted. It has been found 'that oil 

 will spread out even in the direction of the severest wind. 



Although sometimes waves are spoken of as " mountain 



