§ 213-215. THE ATMOSPHERE. 77 



the nortli pole, has blown as the southeast trade-wind. 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 meeting, they are arrested 

 in their course. Here, therefore, there is a calm belt, as well as 

 at Capricorn and Cancer. 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 oper- 

 ation is the reverse of that which took place at the meeting (§210] 

 near the parallel of 30°-35°. 



213. This imaginary particle then, having ascended to the up- 

 The calm belt of P^i* TCgious of the atmosphcrc again, travels there 

 Capricorn. couutcr to the southcast trades, until it meets, near 

 the calm belt of Capricorn, another particle from the south pole ; 

 here there is a descent as before (§ 210) ; it then (§ 211) flows on 

 toward the south pole as a surface w^ind from the northwest. 



214. Entering the polar regions obliquely, it is pressed upon 

 The polar calms and ^J similar particlcs flowiug in oblique currents 

 the return current. r^gpQgg evciy meridian ; and here again is a calm 

 place or node ; for, as our imaginary particle approaches the par- 

 allels near the polar calms more and more obliquely, it, with all 

 the rest, is -whirled about the pole in a continued circular gale ; 

 finally, reaching the vortex or the calm place, it is carried up- 

 ward to the regions of atmosphere above, whence it commences 

 again its reflow to the north as an upper current, as far as the 

 calm belt of Capricorn ; here it encounters (§ 213) its fellow from 

 the north (§ 207) ; they stop, descend, and flow out as surface 

 currents (§ 210), the one with which the imagination is traveling, 

 to the equatorial calm as the soutlieast trade-wind; here (§ 212) 

 it ascends, traveling thence to the calm belt of Cancer as an upper 

 current counter to the northeast trades. Here (§ 210 and 209) it 

 ceases to be an upper current, but, descending (§ 210), travels on 

 with the southwest passage-winds toward the pole. 



215. Now the course we have imagined an atom of air to 

 Diagram of the ^^^c, as ihustratcd by the " diagram of the winds," 

 winds-Plate L jg ^-j-^'g. ^^^ ascent in a place of calms about the 



