Chap. XVII.] THE WINDS AND EVAPORATION. 191 



only come into play when the waters have already 

 been set in motion by other causes ; ^ and, indeed, 

 though the influence of the axial rotation of the 

 earth here referred to accelerates the motion of cur- 

 rents caused by other forces, and determines their 

 direction, or controls them in their course, it is not 

 itself, strictly speaking, a cause of ocean currents at 

 all. Apart, however, from the question as to whether 

 the term cause has been correctly applied in this 

 instance, it is surprising how anyone admitting the 

 action of this mfluence of the axial rotation of the 

 earth — which, indeed, cannot reasonably be denied, — 

 can, nevertheless, at the same time, continue to en- 

 force Major Rennell's theories regarding the causes of 

 ocean currents. Major Rennell had no idea of the 

 existence in the ocean of this influence of the earth's 

 axial rotation which Sir Charles Lyell admits. It has 

 only recently been pointed out by Captain Maury, 

 and is, in fact, incompatible with Major Rennell's 

 theories ; for we have seen, a . few pages back, that, 

 if the waters of the ocean were set in motion from 

 the equator to the poles and from the poles to the 

 equator otherwise than by the action of vis-inertia3, 

 then, that influence of the axial rotation of the earth 

 which Sir Charles Lyell admits would, as it tends 

 eastwards from the equator and westwards to the 



' The reason for Sir Charles Lyell's opinion is, however, that 

 which I have explained in Chapter I. of this volume, it being, of 

 course, a consequence of his acceptance of the ' Laws of Motion.' 



