316 THE CHEMISTRY OF CREATION. 



axle, and therefore the equatorial atmosphere 

 has a more rapid movement through space than 

 that of the poles. If now we suppose a current 



to be dragged across the surface of the earth, 

 from the slowly revolving poles to the rapidly 

 revolving surface of the equator, it is necessarily 

 unable to proceed at once at the same rate as the 

 latter, and the consequence is, that the swiftly 

 moving regions of the earth brush against a 

 mass of air having a slower motion than them- 

 selves. Hence there are two forces to be con- 

 sidered in the production of the trade winds 

 1st, the ascent of a heated equatorial column of 

 air, and 2nd, the resistance offered by a slowly 

 moving current of air proceeding in a horizontal- 

 direction from the poles to the equator. If the 

 earth were stationary, the under current would 



