Ocean Temperatures along the West Coast of North America. 259 



the wind's effect would be limited to a comparatively thin surface 

 layer, even if blowing steadily for any length of time. 



The general circulation of the water in the neighborhood of a 

 coast is shown in (Fig. 7) which represents a cross-section perpendicu- 

 lar to the coast. The wind is assumed to blow parallel to the coast, 

 and normal to the paper from the reader. The arrows show the com- 

 ponents of the velocity of the water in a plane perpendicular to the 

 coast. The actual velocity would be the resultant of that shown and 

 a component parallel to the wind. 



Fig. 7. 

 Cross Section Normal to the Coast. 



If the wind should blow in the opposite direction to that shown, 

 the motion of the water would be reversed. Thus the component of 

 the wind velocity parallel to the coast causes an upwelling of bottom 

 water under the conditions shown, or it carries surface water to the 

 bottom if its direction is reversed. The rate at which water is carried 

 up or down is proportional to the magnitude of the component of the 

 wind velocity parallel to the coast 1 ). 



From a computation of the time required for the stationary motion 

 to be established, the following general conclusions may be drawn. 

 Assuming (D) = 75 meters, the stationary state of motion will be prac- 

 tically fully established to within several hundred kilometers from the 



*) As the depth (d) diminishes from the value of (D) in problems 1 and 2 or 

 diminishes from (2 D) in problem 3 the motion becomes less influenced by the earth's 

 rotation, that is the flow due to a wind tends to have the same direction as the 

 wind, and that due to a pressure gradient tends to flow from a region of high to 

 one of low pressure. But no important alteration in the results worked out above 

 will follow until (d) is less than (0,5 D) in 1 and 2, or less than (D) in 3. 



