Ocean Temperatures along the West Coast of North America. 253 



principles of mechanics, and are therefore independent of any hypothesis 

 as to the laws of fluid friction. 



The following discussion will include only a brief statement of the 

 assumptions made by Ekmann (1), and a few of the most important 

 results that he obtained. It is a well known fact that the rotation of 

 the earth upon its axis tends to deflect (13) a body moving along its 

 surface to the right of its path in the northern hemisphere and to the 

 left in the southern hemisphere. Therefore, in addition to the forces 

 given by the conditions of the problem, this deflecting force must be 

 introduced. It can be proved that a correct solution of a problem con- 

 cerning the motion of a body on the earth's surface will result if we 

 assume no rotation of the earth upon its axis, but introduce the force. 

 1. F = SVwsincj) 



into the equations of motion and solve in the usual w r ay. Velocities 

 and displacements are measured relative to the earth's surface, (V) is 

 the velocity of the body (w) is the angular velocity of the earth, (cP) 

 is the latitude of the place, and (P) is the force perpendular to the 

 direction of motion, as shown in (Fig. 4). 



F 

 Fig. 4. 



That is, the deflecting force due to the earth's rotation is pro- 

 portional to the velocity of the body relative to the earth's surface and 

 increases from zero at the equator to a maximum at the poles, and 

 for a horizontal velocity in any direction is directed normally to the 

 motion. (Fig. 4) corresponds to the northern hemisphere, but the arrow 

 (F) would have to be reversed to correspond to the southern hemisphere. 



First typical problem. Imagine a large ocean of uniform depth 

 and without differences of density affecting the motion of the water. 

 The influence of neighboring ocean currents and continents is left out 

 of account so that water can freely flow in or out of the region con- 

 sidered. Suppose the water surface to be impelled by a steady and 

 uniform wind equal in strength and in direction over the whole region, 



