438 HENRY M. EAKIN 



and the ellipticity of the earth, being more than a match for it, the 

 object would tend to sHde down the gradient toward the poles, to 

 the right in the northern hemisphere, with respect to the direction 

 of its relative motion, and in the southern hemisphere to the left. 

 These principles do not require that the object move directly east 

 or west, but operate so long as there is an easterly or westerly com- 

 ponent in its relative motion. 



Component of F^ Arising from North-and-South 

 Relative Motion 



Another component of the deflecting force of the earth's rotation 

 arises when the relative motion is in a northerly or southerly direction. 

 Suppose an object at rest with respect to the earth's surface at a 

 latitude of parallel A be acted upon by a force causing it to move to 

 a higher latitude of parallel B. At parallel A the object had a certain 

 gyratory velocity corresponding with a point in the circle A. Being 

 drawn toward the center of gyration in moving to a smaller circle, 

 this gyratory velocity is accelerated according to the law of conserva- 

 tion of angular momentum. And since the gyratory velocity of a 

 point in Circle B is less than that of a point in Circle A, and the 

 gyratory velocity of the object is greater than that of a point in Circle 

 A, the object has come to have a gyratory velocity very different from 

 the earth's surface at the same latitude. 



This difference would give the object a relativ^e motion in an 

 easterly direction, to the right in the northern hemisphere and in the 

 southern hemisphere to the left. 



If the object were at rest at Circle B and were caused to move to 

 Circle A, the reverse of the above case would be true. The actual 

 gyratory velocity of the object would be decreased according to the 

 same law, and the earth's surface would have a higher velocity at 

 Circle A than at Circle B. The object would have gained a negative 

 component of velocity in a westerly direction with respect to the 

 earth's surface, and, as before, the deviation would be to the right 

 in the northern hemisphere and to the left in the southern. In either 

 case should the object have, at the start, a relative motion, the same 

 principles would be effective. 



