FROM THE POLES BECOME EASTERLY. 210 



earth is the same — to blow in the opposite direc- 

 tion, namely, from east to west. The rate of 

 motion in the westward direction, which the wind 

 acquires in this manner, is certainly very much 

 diminished by the manifold resistances winch it 

 meets with from the earth's surface ; and therefore 

 the lower trade-wind seldom has a greater speed 

 than fifteen feet per second. Nevertheless the 

 original polar direction must pass more into a 

 westward one (that is, the wind must become more 

 easterly), the greater the difference of the latitude 

 of the place, from which the wind began its move- 

 ment towards the equator, from that of the spot at 

 winch it is observed. 



From this you will readily understand why the 

 currents which start at the northern hemisphere 

 as northerly winds, must, as they advance south- 

 wards, pass gradually through a north-easterly 

 direction into one more nearly from the east ; and 

 why, again, in the southern hemisphere, the winds 

 which in like manner set out from the south must 

 become first south-easterly, and then more and 

 more easterly, in their progress northwards. 



Currents of air, winch flow in the direction from 

 the equator to the poles, must behave in an 

 exactly contrary manner. They come from regions 

 moving with greater speed round the earth's axis 

 — a speed winch they share themselves — to higher 

 latitudes \ that is, to regions moving round at a 



