Q4 TRAE-wiNCi__ [Lesson XVII. 



from both hemispheres towards the equator, as they 

 advance, are constantly deflected more and more 

 towards the east, by reason of the earth's rotation j 

 that from the southern hemisphere originally a 

 south wind, is made to veer more and more towards 

 the east : in like manner, that from the northern 

 hemisphere is made to change its direction from the 

 north towards the east. These two masses meeting 

 near the equator, their velocities south and north 

 destroy each other, and they proceed afterwards 

 with their common velocity from east to west 

 round the torrid zone, excepting the irregularities 

 produced by the continents. The equator is not 

 in reality the place of concourse, but the northern, 

 parallel of four degrees : because the centre of heat 

 is thereabouts, the sun being no longer on the north 

 side of the equator than on the south side. More- 

 over, when the sun is near one of the tropics, the 

 centre of heat upon the earth's surface is then 

 nearer that tropic than usual, and therefore the 

 winds about the tropic are more nearly east at that 

 time, and those about the other tropic more nearly 

 north and south. 



If all the terrestrial globe were covered with 

 water, or, if the variations of the earth's surface in 

 heat were regular and constant, so that the heat 

 was the same in every part of the same parallel of 

 latitude, the winds would then be very nearly re- 

 gular also. But this is not the case : for we find the 

 irregularities of heat, arising from the interspersion 

 of land and sea, are such, that though all the 1 parts 

 of the atmosphere in some measure conspire to 



produce 



