THE WINDS. 227 



ing their return to the south. But, though he would observe 

 (§ 131) that they follow the sun m his annual course, he would 

 remark that they do not change their latitude as much as the sun 

 does his declination ; he would, therefore, discover that their ex- 

 tremes of declination are not so far asunder as the tropics of Can- 

 cer and Capricorn, though in certain seasons the changes from day 

 to day are very great. He would observe that these zones of 

 winds and calms have their tropics or stationary nodes, about 

 which they linger near three months at a time ; and that they pass 

 from one of their tropics to the other in a little less than another 

 three months. Thus he would observe the whole system of belts 

 to go north from the latter part of May till some time in August. 

 Then they would stop and remain stationary till winter, in Decem- 

 ber ; when again they would commence to move rapidly over the 

 ocean, and down toward the south, until the last of February or 

 the first of March ; then again they would become stationary, and 

 remain about this, their southern tropic, till May again. 



488. The Horse Latitudes. — Having completed the physical 

 examination of the equatorial calms and winds, if the supposed ob- 

 server should now turn his telescope toward the poles of our earth, 

 he would observe a zone of calms borderinsc the northeast trade- 

 winds on the. north (§ 100), and another bordering the southeast 

 trade-winds on the south (§ 106). These calm zones also would 

 be observed to vibrate up and down with the trade-wind zones, 

 partaking (^ 130) of their motions, and following the declination 

 of the sun. 



On the polar side of each of these two calm zones there would 

 be a broad band extending up into the polar regions, the prevail- 

 ing winds within which are the opposites of the trade- winds, viz., 

 southwest in the northern and northwest in the southern hemi- 

 sphere. 



489. The equatorial edge of these calm belts is near the tropics, 

 and their average breadth is 10° or 12°. On one side of these 

 belts (^ 101) the winds blow perpetually toward the equator; on 

 the other, their prevailing direction is toward the poles. They are 

 called (^ 101) the *' horse latitudes" by seamen. 



490. Along the polar borders of these two calm belts (^ 129) 

 we have another region of precipitation, though generally the rains 

 here are not so constant as they are in the equatorial calms. The 



