MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 113 



the air. At any rate, here is proof of the immense quantity of 

 vapor which these winds of the extra-tropical regions carry along 

 with them toward the poles ; and I can imagine no other place 

 than that suggested, whence these winds could get so much vapor. 

 I am not unaware of the theory, or of the weight attached to 

 it, which requires precipitation to take place in the upper regions 

 of the atmosphere on account of the cold there, irrespective of 

 proximity to mountain tops and snow-clad hills. 



But the facts and conditions developed by this system of re- 

 search upon the high seas are in many respects irreconcilable 

 with that theory. With a new system of facts before me, I have, 

 independent of all preconceived notions and opinions, set about to 

 seek among them for explanations and reconciliations. 



These may not in all cases be satisfactory to every one ; in- 

 deed, notwithstanding the amount of circumstantial evidence that 

 has already been brought to show that the air which the north- 

 east and the southeast trade-winds discharge into the belts of 

 equatorial calms, does, in ascending, cross — that from the southern 

 passing over into the northern, and that from the northern pass- 

 ing over into the southern hemisphere (see F and G, B and C, 

 Plate I.) — yet some have imphed doubt by asking the question, 

 *' How are two such currents of air to pass each other ?" And, 

 for the want of light upon this point, the correctness of reasoning, 

 facts, inferences, and deductions have been questioned. 



205. In the first place, it may be said in reply, the belt of equa- 

 torial calms is often several hundred miles across, seldom less than 

 sixty ; whereas the depth of the volume of air that the trade-wiads 

 pour into it is only about three miles, for that is supposed to be 

 about the height to which the trade-winds extend. 



Thus we have the air passing into these calms by an opening 

 on the north side for the northeast trades, and another on the south 

 for the southeast trades, having a cross section of three miles ver- 

 tically to each opening. It then escapes by an opening upward, 

 the cross section of which is sixty or one hundred, or even three 

 hundred miles. A very slow motion upward there will carry off 

 the air in that direction as fast as the two systems of trade-winds, 

 with their motion of twenty miles an hour, can pour it in ; and 

 that curds or columns of air can readily cross each other and pass 

 in different directions without interfering the one with the other, 



H 



