THE ATMOSPHERE. 
73 
directions at the bottom, the motion of the water would be down- 
ward, so is the motion of the air in this calm zone. 
102. The barometer, in this calm region, is said to stand higher 
than it does either to the north or to the south of it ; and this is 
another proof as to the banking up here of the atmosphere, and 
pressure from its downward motion. 
103. Following our imaginary particle of air from the north 
across this calm belt, we now feel it moving on the surface of the 
earth as the northeast trade-wind; and as such it continues, till it 
arrives near the equator, where it meets a like hypothetical par- 
ticle, which, starting from the south at the same time the other 
started from the north pole, has blown as the southeast trade-wind. 
104. Here, at this equatorial place of meeting, there is another 
conflict of winds and another calm region, for a northeast and 
southeast wind can not blow at the same time in the same place. 
The two particles have been put in motion by the same power ; 
they meet with equal force ; and, therefore, at their place of meet- 
ing, are stopped in their course. Here, therefore, there is a qalm 
belt. > 
105. Warmed now by the heat of the sun, and pressed on each 
side by the whole force of the northeast and southeast trades, 
these two hypothetical particles, taken as the type of the whole, 
cease to move onward and ascend. This operation is the reverse 
of that which took place at the meeting 100) near the parallel 
of 30°. 
106. This imaginary particle then, having ascended to the up- 
per regions of the atmosphere again, travels there counter to the 
southeast trades, until it meets, near the calm belt of Capricorn, 
another particle from the south pole ; here there is a descent as 
before 101); it then 98) flows on toward the south pole as 
a surface wind from the northwest. 
Entering the polar regions obliquely, it is pressed upon by sim- 
ilar particles flowing in oblique currents across every meridian ; 
and here again is a calm place or node ; for, as our imaginary par- 
ticle approaches the parallels near the polar calms more and more 
obliquely, it, with all the rest, is whirled about the pole in a con- 
tinued circular gale ; finally, reaching the vortex or the calm place, 
it is carried upward to the regions of atmosphere above, whence 
it commences again its circuit to the north as an upper current, as 
