It is further supposed that, when they reach the poles, they ‘whirl about’ them, ascend, become upper currents again, and start back to the 30th parallel; and that, when they have returned to this parallel, they descend, become a surface current again—in other words, the trade—wind-and proceed to the equator as before.
But there is another, and more beautiful problem still, connected with these winds.
It is their crossing each other at the equator, of which the proofs are so abundant, that there can be but little doubt concerning it. And yet the proposition, looked at apart from the proofs, is a very startling one. One would think that when the two winds met at the equator, there would be a general intermingling, and confounding of particles, and that when they ascended to form the upper currents, of which I have spoken, the northern particle would be