168 THE OCEAN. [Book VII. 



of the earth — does, hi fact, necessitate a current - 

 creating action m the plane of the equator as far as 

 the axial rotation of the earth is concerned : and that 

 it admits of a current-creating action m the plane of 

 the ecliptic, as far as the orbital motion of the earth 

 is concerned, at a velocity of more than sixty miles a 

 day. 



I do not, however, by any means suppose that I 

 have replied completely to the sense in which the 

 objection is intended to be understood. The objection 

 appears to be twofold. 



One of the objections intended appears to be, that 

 since the velocity of the earth's orbital motion is 

 more than sixty times greater than that of its axial 

 rotation, therefore, if the atmospheric currents said 

 to be caused by axial rotation really were so, there 

 ought then to be far more manifest effects resulting 

 from orbital motion. But in reply to this I have 

 shown, in Chapter III., that the current- creating 

 action of vis -inertia depends on the differences in 

 the force of its action in different parts of the ocean 

 (or atmosphere), and that, in consequence of this, the 

 current-creating action of axial rotation is far greater 

 than that of orbital motion. 



And if, instead of the literal sense of the objections 

 above refuted, it be asserted that the ocean and 

 atmosphere are held in their positions, in relation to 

 that part of the surface of the earth on ivhich they rest, 

 by gravitation, and that no action of vis-inertiaa can 



