On, on, on, rapidly the Genius flew. A golden cloud appeared. The two clouds met, but so softly, that there was no commotion. Attracted by the globe, probably, they both descended, slowly followed by the Genius and the boy, till once more the earth appeared in sight, clothed with the palm-tree, the orange, the pomegranate, the vine, and numberless tropical fruits and flowers.
“We have reached a calm region, the tropic of Cancer,” said the Genius. “Now watch the earth. It is turning from west to east, while we move on in the direct line in which we started, so that we appear to be crossing the globe diagonally, and to the inhabitants of the earth that silvery cloud appears to be coming from the north-east, and going to the south-west. That silvery cloud is merely a portion, made visible to your eye, of a great mass of air, which is continually blowing, and which the inhabitants of the earth, from the facilities it affords their commerce, call the north-east trade-wind. Now see a golden cloud approaching us; that is a mass of air coming from the southern pole. We are arriving near the Equator. See, the two clouds meet. They have an equal impetus; neither can give way, but, gently and noiselessly pressed together, they rise to a higher stratum of the atmosphere.”
On floated the boy and his guide, far up above the globe, still on, in rather a less direct line than before, till again a golden cloud was met, and gently that, and the cloud they followed, descended till the earth was seen once more.
“We have reached the tropic of Capricorn, where these two opposing currents form a calm, almost continuous, except when certain interposing causes break it, and which I may hereafter explain to you.” Passing out of the calm region, away they floated towards the southern pole.
“Remark,” observed the Genius. “The silvery cloud, having been pressed down by that other current from above, has a south-eastern direction given to it, and therefore appears to the people on earth to be coming, not from the north, but from the north-west.”
A wide extent of ocean was seen beneath their feet. On they floated. Then fields of ice and icebergs, and wide extended lands covered with snow, and vast mountains of ice. Once more they moved on, slowly as before.
“We are at the antarctic pole,” said the Genius. “See, our cloud of silver meets another of gold, pressing gently.” Up, up, they mount. “Once more we will move towards the tropic of Capricorn, high up above the globe. Now we descend in that calm region; and now close to the earth we are moving on. But see, coming from the southern pole, the globe moves as before, from west to east; and thus this mass of air, of which our silvery cloud, remember, is but a portion, seems to those on the earth to be coming from the south-east. As this wind is always blowing, and as ships by getting within its influence are borne easily forward, and it thus facilitates commerce, it is called the south-east trade-wind.”
On they went, till again the calms of the equator were reached, or rather, till the air, exhausted by its long course, met another gentle current, and the two pressing together rose upwards, the silvery cloud going on towards the tropic of Cancer, till forced by another current, known by its golden hue, to descend, it went on close to the earth towards the northern pole, where a calm, caused by another gentle current meeting it, was created. Gently pressed up, however, the silvery cloud finally reached the higher region, whence the Genius and the boy had started with it on its long journey.
“Had we started with the golden cloud, or rather with the mass of air which that cloud represents, from the southern pole, we should have seen precisely the same effects produced,” said the Genius. “You now understand what mortals call the theory of the trade-winds. You read in the sacred word of God, which in his mercy and goodness he gave to men to guide them in their passage through life, that, ‘The wind goeth toward the south, and turneth about unto the north; it whirleth about continually, and the wind returneth again according to his circuits’ (Eccles. i. 6). Now, boy, you have seen how true and beautiful is that account written by the wise king of Israel.” The boy listened attentively. “We will fly back to the equatorial calms,” said the Genius; “see what effect the direct rays of the sun have on the earth, or that portion of its surface. They affect the air likewise; heat expands it, and then makes it rise; and it also changes its specific gravity. Cold contracts it, and also changes its specific gravity. These two causes are unceasingly at work to produce the currents of air whose courses we have been observing. The heat of the sun at the equator expands the air, and thus it rises and flows north and south; having arrived once more at the tropics, owing to the counter current it meets, it descends, as we saw, and flowing along near the earth, receives from it a rotatory motion, which increases as it approaches the pole, where, contracted by the cold, it masses into a dense body, and ultimately is whirled upwards, forming an ascending column, when it once more commences its never-ceasing journey.”
As they flew towards the mountain whence they set out, the boy expressed his thanks to the Genius; if he did not comprehend all that she had shown him and told him, he knew more about the matter than he had before done. She saw by the expression of his countenance the gratification he had enjoyed. “’Tis well,” she continued; “as a drop of water is to the ocean which lies beneath us, so is the knowledge you may obtain in a lifetime to the wonders nature has to reveal. You desire to know more; gladly will I show you more. Whenever you climb up to this rocky height I will meet you, as I have done to-day, and each time unfold new wonders to your view. Ah, you think that I might descend to you, without making you toil up the mountain; but know that knowledge will not come to you; you must exert yourself, you must labour to attain it. You say that you will willingly climb the height. That is well. That is the spirit which ensures success. Return to your companions. They will not have missed you.”