134 WAVES OF THE SEA 



that it never remains stationary for more than one 

 or two seconds, but is continually shifting through 

 a large angle. 



Another cause can also be divined for the unlevel 

 tops of the wave -ridges and their small lateral ex- 

 tension. This cause is a greater force of wind to 

 right or left of the ship's course. Suppose, in the 

 first place, that the ship is in a calm, and that to the 

 starboard and in front there is a head wind blowing. 

 Then a swell will spread out laterally from that 

 area, meeting the ship obliquely on the starboard 

 quarter. Secondly, if a lighter head wind be blow- 

 ing where the ship is, the wind-waves will be crossed 

 obliquely by this swell from the starboard, even 

 though the wind there be blowing in the same 

 direction as that where the ship is. The velocity 

 of the wind being less where the ship is, it will 

 not be able to regularise the obliquely-running, 

 swifter swell. 



The wind -formed waves which run in the most 

 regular ridges (i.e., of the greatest lateral exten- 

 sion as compared to their wave length) are of two 

 orders of magnitude. First, the small waves of a 

 few feet in length and not more than one foot 

 high; second, the large ocean waves. The regu- 

 larity of the first is not affected by long-period 

 veering of the wind, for they die out completely in 



