SPEED AXD HEIGHT OF WAVES. 447 



where they are generally long and low. But 

 when the stormy wind arises in its power, their 

 height and magnitude constitute one of the 

 grandest displays of elemental motion and 

 power in the world. For measuring the height 

 of waves the following plan has been most fre- 

 quently pursued: When the ship is in the 

 trough of the sea, the person observing ascends 

 the rigging, until he can just see the crest of 

 the coming wave on a level with the horizon; 

 and the height of his eye above the ship's 

 water-line will give a very fair measure of the 

 difference of level between the crest and hollow 

 of a sea; deducting half from this for the de- 

 pression of the hollow below the general level 

 of the surface, we obtain in the remainder the 

 perpendicular height of the wave. It is con- 

 sidered by some that the utmost elevation of 

 waves produced by the action of the wind does 

 not exceed twelve feet. Others state their 

 occasional height at twenty feet. Few persons 

 can realize the magnificent effect of standing 

 on the cliffs of the west coast of Ireland, and 

 observing the great breakers rolling in from the 

 Atlantic, some of which have been ascertained, 

 by the method described, to be fifty feet high, 

 and occasionally they even reached the enor- 

 mous magnitude of 150 feet. 



In addition to the oscillatory gregarious waves, 



