ENVELOPING this solid globe of ours are two oceans-one partial, the other universal. There is the ocean of water, which has settled down into all the depressions of the Earth"s surface, leaving dry above it all the high lands-as mountain-ranges, continents, and islands; and there is an ocean of air, which inwraps the whole in one transparent mantle. Through the bosom of that ocean, like fishes with their fins and whales with their flippers, birds and other winged creatures swim; whilst, like crabs and many shellfish, man and other mammalia creep about at the bottom of this a?rial sea.
The air-ocean, which everywhere surrounds the Earth, and feeds and nourishes it, is even more simple, more grand, and more majestic than the "world of waters"-more varied and changeful in its moods of storm and calm, of ebb and flow, of brightness and gloom. The atmosphere is,indeed, a wonderful thing-a most perfect example of the economy of nature. Deprived of air, no animal would live, no plant would grow, no flame would burn, no light would be diffused. The air, too, is the sole medium of sound. Without it, mountains might fall, but it would be in perfect silence-neither whisper nor thunder would ever be heard.
The atmosphere is supposed to become inappreciable at the height of between forty and fifty miles from the Earth.
A philosopher of the East, with a richness of imagery truly Oriental, thus describes it: -"It surrounds us on all sides, yet we see it not; it presses on us with a load of fifteen pounds on every square inch of surface of our bodies, or from seventy toone hundred tons on us in all, yet we do not so much as feel its weight. Softer than the softest down, more impalpable than the finest gossamer, it leaves the cobweb undisturbed, and scarcely stirs the slightest flower that feeds on the dew it supplies; yet it bears the fleets of nations on its wings around the world, and crushes the most refractory substances with its weight.
"When the air is in motion, its force is sufficient to level the most stately forests and stable buildings with the earth; to raise the waters of the ocean into ridges like mountains, and dash the strongest ships to pieces like toys. It warms and cools by turns the Earth, and the living creatures that inhabit it. It draws up vapours from the sea and the land, retains them dissolved in itself, or suspended in cisterns of clouds, and drops them down again, as rain or dew, when they are required. It bends the rays of the sun from their path, to give us the twilight of evening and of dawn; it disperses and refracts their various tints to beautify the approach and the retreat of the orb of day.
"But for the atmosphere, sunshine would fail us at once; and, on the other hand, at once remove us from midnight darkness to the blaze of noon. We should have no twilight to soften end beautify the landscape, no clouds to shade us from the scorching heat; but the bald Earth, as it revolved on its axis, would turn its tanned and weakened front to the full andunmitigatedrays of the lord of day. It affords the gas whichvivifies and warms our frames, and receives into itself that which has been polluted by use and is thrown off as noxious. It feeds the flame of life exactly as it does that of the fire; -it is in both cases consumed, and affords the food of consumption; in both cases it becomes combined with charcoal, whichrequires it for combustion, and which is removed by it when this is over.""It is only the girdling, encircling air," says another philosopher, "flowing above and around all, that"makes the whole world kin." The carbonic acid with which today our breathing fills the air, to-morrow seeks its way round the world. The date-trees that grow around the falls of the Nile will drink it in by their leaves; the cedars of Lebanon will takeof it to add to their stature; the cocoa-nuts of Tahitiwillgrow rapidly upon it; and the palms and bananas of Japan will change it into flowers.
The oxygen that we are breathing was distilled for us some short time ago by the magnolias of the Susquehanna, and the great trees that skirt the Orinoco and the Amazon;- the giant rhododendrons of the Himalayah contributed to it, and the roses and myrtles of Cashmere, the cinnamon-trees of Ceylon, and the forest, older than the Flood, buried deep in the heart of Africa. The rain we see descending was thawed forus out of the icebergs which have watched the polar star for ages; and the lotus lilies have sucked up from the Nile, and exhaled as vapour, snows that rested on the summits of the Alps.
"The atmosphere, which forms the outer surface of the habitable world, is a vast reservoir, into which the supply of food designed for living creatures is thrown; or, in one word, it is itself the food, in its simple form, of all living creatures. The animal grinds down the fibre and the tissue of the plant,and the nutritious store that has been laid up within its cells, and converts these into the substance of which its own organs are composed. The plant acquires the organs and nutritious store, thus yielded up as food to the animal, from the air surrounding it. "But animals are furnished with the means of locomotion and of seizure: they can approach their food, and lay hold of and swallow it. Plants must wait till their food comes to them. No solid particles find access to their frames. The restless ambient air, which rushes past them, loaded with the carbon, the hydrogen, the oxygen, the water, everything they need in the shape of supplies, is constantly at hand to minister to their wants; not only to afford them food in due season, but in theshape and fashion in which alone it can avail them."There is no employment more ennobling to man and his intellect than to trace the evidences of design and purpose in the Creator, which are visible in all parts of the creation. Hence, to him who studies the physical relations of earth, sea, and air, the atmosphere is something more than a shoreless ocean, at the bottom of which he creeps along.
It is an envelope or covering for dispersing light and heatover the surface of the Earth; it is a sewer,into which, withevery breath we draw, we cast vast quantities of dead animal matter; it is a laboratory for purification, in which that matter is recompounded and wrought again into wholesome and healthful shapes; it is a machine for pumping up all the rivers from the sea, and conveying the waters from their fountains in the ocean to their sources in the mountains; it is an inexhaustible magazine, marvellously adapted for benign and beneficent purposes.
- MAURY
QUESTIONS
Name the two oceans which envelop the globs. What effects would follow if the globe were deprived of air? With what weight does it press upon our bodies? What is its force able to do when it is in motion? How does twilight depend upon it? How does it "make the whole world kin"? Of what is the atmosphere a vast reservoir? Wherein do plants differ from animals is regard to food? How does the air minister to plants? Why may the atmosphere be compared to a sewer? Why to a laboratory? Why to a pumping-machine?