258 



G. F. McEwen. 



Third typical problem. Assume a steady uniform wind blowing 

 in a constant direction everywhere outside a straight and infinitely long 

 coast. Under these conditions, the depth of the ocean being supposed 

 uniform, the current would be the same at any two places at the 

 same distance from the coast, and no inclination of the surface can 

 occur in the direction of the coast itself. Perpendicular to this direction 

 a slope will arise and gradually increase until the total flow normal to 

 the coast is zero. If the depth exceeds (2 D) there will be three 

 distinct currents: first, a "bottom-current" of depth (D) moving more or 

 less in the direction of the slope, but with a deflection to the right 

 increasing from 45 at the bot tomto 90 at the top: second, a "mid- 



water-current" of almost uniform velocity parallel to the coast and 

 reaching from the top of the "bottom-current" to the depth (D) below 

 the surface. (The velocity of this current is proportional to the com- 

 ponent of the wind velocity parallel to the coast): third, a "surface- 

 current" in which the volocities are equel to those of a wind- 

 current" superposed on the velocity of the "midwater- current" w The 

 bottom - current" and the "surface-current" will not be appreciably in- 

 fluenced by an alteration of the depth (d) as long as it exceeds (2D), 

 and the only effect then will be a corresponding alteration of the 

 depth of the uniform "mid water-current". 



The most striking result of the coast's influence is that a wind is 

 able indirectly to produce a current more or less in its own direction 

 from the surface down to the bottom, while in the absence of coasts 



