THE WINDS. 227 
iilg^ their return to the south. But, though he would observe 
(§ 131) that they follow the sun in his annual coifrse, 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 House 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 bordering 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 dechnation 
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 oth'er, 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 
