Raphael Semmes, Memoirs of Service Afloat During the War Between the States

[504] as likely to turn back to the north, as to cross the equator and go South. The preceding figure will illustrate the crossing. Let a represent the equator, the arrows near the surface of the circle the two trade-winds, and the two cross arrows, two particles of wind in the act of crossing. The difficulty is to conceive how these particles should cross, without mixing with each other, and losing their identity; or why they should not turn back, as well as continue their course. What law of nature is it, that makes the particles of atmosphere which have come from the north pole, so separate and distinct from those which have come from the South pole, as to prevent the two from fusing, and becoming one? is it because the two particles, as they have gyrated around their respective poles, have received a repulsive polarity? whatever may be the reason, there can be no doubt, as remarked, that they do actually cross. One strong proof of their crossing is, that we cannot conceive, otherwise, how the great atmospheric machine could perform its office of distributing rain over the earth in due proportions. The reader will recollect that there is from a fourth, to a third, more land than water, in the northern hemisphere, and that there is from a fourth to a third more water than land in the southern hemisphere. The consequence of this unequal distribution of land and water in the two hemispheres is, that the northern hemisphere requires more rain than the southern, in the proportion in which it has more land to be rained upon. Now it is these mysterious trade-winds, of which we have been speaking, that are the water-carriers of the two hemispheres. These winds, on their way to the equator, generally reach the 30th parallel as dry winds. These dry winds, sweeping over the tropical seas, take up, in the shape of vapor, the water with which, in due time, they are to fertilize the fields of the farmer, and make the rose blossom. The quantity which they take up is in proportion to the sea-surface, or evaporating surface, they have respectively passed over. Now, if we will examine the jars of these water-carriers, when they reach the equator, we shall find that the northern jars are not nearly so full as the southern jars; the reason being, that the northern winds have passed over less evaporating surface.