MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. II3 
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-winds 
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 cu?'ds or columns of air can readily cross each other and pass 
in different directions without interfering the one with the other, 
H 
