counsel, and excellent in working"-"his ble, and the ways of his providence "past wisdom is unsearchable," his power irresisti- finding out."

CHAPTER VII.

The Beneficial Effects of the Atmosphere in the System of Nature.

THIS subject presents an immense field of From the various proportions in which these contemplation, which it would require several ingredients are combined, results almost all volumes fully to illustrate: and, therefore, a the variety of vegetable matters which fall few general statements and illustrations can under our notice. To the atmospheric influence, therefore, we

only be given.

them again, thus keeping up a perpetual motion of their juices. It has likewise been ascertained, from recent experiments, that the pressure of the atmosphere has a powerful influence on vegetation, which suggests to us one of those causes which prevent trees from flourishing on the elevated. sides of lofty

1. In the first place, air is essentially re- are indebted for all the productions of our quisite to the germination and growth of fields and gardens, and for all that diversity of plants; and, therefore, to the influence of prospect and colouring which the vegetable atmospheric air all the beauties of the vegeta- tribes spread over the landscape of the world. ble creation are to be chiefly ascribed. By It is true, indeed, that water is also necessary experiment, it is found that the access of at for the production of plants. But what is mospheric air is no less necessary for plants water? It is nothing else than a composition: than it is for the continuation of animal life. of two kinds of air, oxygen and hydrogen, Like animals they are found to die when con- combined in certain proportions. Now, it is fined within a vacuum, or deprived of the found that plants have the power of decomvital air. The influence of the atmosphere posing water into these two principles, throwis equally essential at every period of their ing off a part of the one, and absorbing a part existence, from the germination of their seeds of the other. The elasticity of the air has to the full development of all their organs in likewise an important influence on the airthe perfect plant. Their leaves, acting in vessels of vegetables; for the contained air, some measure like the lungs of animals, ab- alternately expanding and contracting, accordsorb oxygen gas during the night, and carbo- ing to the increase or diminution of the heat, nic-acid gas during the day; and this alternate alternately presses the vessels, and eases process is found to be essential to their growth and nourishment. Even the green colour of plants, which is produced chiefly by the influ ence of light, is proved not to be perfected without the co-operation of oxygen gas. It is found that pure air, or oxygen gas, may be procured by putting the leaves of plants into water, and exposing them to the sun. In mountains. purifying contaminated air, Dr. Priestley dis- 2. The pressure of the atmosphere has an covered that vegetables answered this purpose influence in preserving water in the state in most effectually. Having rendered a quan- which we find it. Nothing is of more importity of air very noxious, by mice breathing tance to the comfort of man and other crea and dying in it, he divided it into two re- tures, and to almost all the processes of the ceivers, inverted in water, introducing a arts, than water-without which our globe sprig of mint into one of them, and keeping would be transformed into an immense desert. the other receiver, with the contaminated air But, if there were no atmosphere, all the wain it, alone. He found, in about eight or ters on the face of the earth would boil, and nine days after, that the air of the receiver be evaporated with a very slight degree of into which he had introduced the sprig of heat. The ocean would be drained to its mint had become respirable; for a mouse lowest caverns, the rivers would cease to flow, lived very well in this, but died immediately the springs would be dried up, and the whole upon being introduced into the other receiver, surface of the land exhausted of that moisture containing the contaminated air alone. It is so essential to the existence of the animal and: likewise proved by experiment, that the simple vegetable world. Indeed, it is not improbable, component principles which are essential to that all the substances on the earth, solid as the formation of vegetable matter are but well as fluid, would be dissipated into vapour. three in number, namely, carbon, oxygen, and That such effects would actually take place, hydrogen; and these form the bases of car- appears from a variety of experiments. If we bonic acid gas, oxygen gas, and hydrogen gas, fill a long-necked bottle with boiling water.

and cork it close, so as to exclude the air, and that respiration of all animals depends. The place it in a basin of cold water, the water process of respiration is carried on by means will sink in the neck of the bottle as it cools. of the lungs. These are distinguished into This shrinking of the water will produce a right and left. The right, or larger lung, is vacuum in the upper part of the bottle, and divided into three lobes; the left, or smaller, the water within it will be seen to re-com- into two. The internal fabric of the lungs is mence boiling with great violence, which can composed of an infinite number of small arise from nothing but the cork taking off the membranous cells, full of air, communicating pressure of the atmosphere from the water. with one another, the number of which Dr. În like manner, if we place water that has Keil and other anatomists have computed to been cooled several degrees below boiling, be at least 1,744,000,000, that is, one thouunder the receiver of an air-pump, it will sand seven hundred and forty-four millions. begin to boil as soon as the air is exhausted. The air from without rushes into these vesiIt requires a heat of 212° of Fahrenheit's cles, and is again expelled 1,200 times every thermometer to make water boil under the hour: and during the same time we consume common pressure of the atmosphere; but in about 48,000 cubic inches of air, or, at the the exhausted receiver of an air-pump, it boils rate of seventy-seven wine hogsheads in a when heated to only about 67°. The pheno- day. The chief uses of respiration are-1, menon exhibited by what is called the pulse- to bring the blood in contact with the air; 2, glass, is also owing to the same cause. This to effect certain changes in the mass of the glass, having two bulbs, is partly filled with blood; and 3, to produce animal heat. Acspirits of wine, the air is extracted, and the cordingly, the lungs are so constructed as to glass hermetically sealed; and when the hand allow the largest possible quantity of deteriois applied to one of the bulbs, it causes a heat rated blood to enjoy the fullest intercourse which produces an ebullition in the spirits of with the largest possible quantity of vital air. wine. It is likewise owing to this pressure It has been calculated by Dr. Hales, that each that porter, ale, and other fermented liquors air-cell is the one-hundredth part of an inch are preserved in bottles; without which they in diameter, and that the amount of surface would either rush with violence out of their mouths, or burst them to pieces. It is owing to the same power that boiling water is preserved in our pots and kettles, when used in cooking, without the influence of which it would soon dilate itself, rush over the vessels, and be dissipated into vapour.

furnished by them, collectively, is equal to twenty thousand square inches. Others have estimated the surface to be more than 1500 square feet; and Dr. Monro states, that it is thirty times the surface of the human body. From numerous experiments, it has been found that the blood perpetually receives oxygen gas 3. It is to the atmosphere we are indebted from the atmosphere by the agency of the for the action of fire and flame. Fire is es- lungs, and that its red colour is derived from sentially necessary to human existence, even this source. The blood is purple when it ar in the warmest climates of the globe. By its rives at the lungs from the heart; but, having means the inhabitant of the desert frightens there thrown off hydrogen and carbon, it imfrom his dwelling the beasts of prey, and bibes the vital air of the atmosphere, which drives away the insects which thirst for his changes its dark colour to a brilliant red, renblood. By its means also, man, in every dering it the spur to the action of the heart country, prepares his food, dissolves the me- and arteries, and the source of motion and of tals, vitrifies rocks, hardens clay, softens iron, animal heat. The blood is thus indebted tempers steel, and gives to all the productions every moment to the invigorating influence of of the earth the form and combinations which the atmosphere, without which the heart his comfort and necessities require. But, would cease to beat, the circulating fluids without the vital air, no flame can be extri- would stagnate, and the body become a cold cated, nor fire made to burn. This is proved by putting a burning taper within the receiver The following are some of the results of exof an air-pump, and when the air is extracted periments in relation to this subject, lately it is instantly extinguished. The act of com- performed by Dr. S. Smith. "1. The volume bustion effects an analysis of the air; it sepa- of air ordinarily present in the lungs is twelve rates its component parts: the oxygen of the English pints. 2. The volume of air received atmosphere combines with the combustible by the lungs at an ordinary inspiration, is one body; caloric, in the form of sensible heat, is pint. 3. The volume of air expelled from the thrown off in every direction; and therefore, lungs at an ordinary expiration, is a little less where no oxygen exists, it is impossible to than one pint. 4. Of the volume of air remake even the most combustible body produce ceived by the lungs at one inspiration, only beat or flame. one-fourth part is decomposed at one action 4. It is on the influence of the atmosphere of the heart, and this is so decomposed, in the

putrid mass, without sensibility or motion.

five-sixth parts of one second of time. 5. The blood circulates through the system, and returns to the heart in one hundred and sixty seconds of time, which is exactly the time in which the whole volume of air in the lungs is decomposed. These circuits are performed every eight minutes; five hundred and forty circuits are performed every twenty-four hours. 6. The quantity of blood that flows to the lungs, to be acted upon by the air at one action of the heart, is two ounces, and this is acted upon in less than one second of time. 7. The quantity of blood in the whole body of the human adult is twenty-four pounds avoirdupois, or twenty pints. 8. In twentyfour hours, twenty-four hogsheads of blood are presented to the lungs, to receive the influence of the vital air. 9. In the mutual action which takes place between the quanti ties of air and blood which come in contact in twenty-four hours, the air loses three hundred and twenty-eight ounces of oxygen, and the blood ten ounces of carbon."

no free communication with the air, they are soon deprived of existence.

5. The atmosphere is the medium in which the process of evaporation is carried on, and in which clouds, rain, and dew are produced. By the heat of the sun and other causes, an immense portion of matter is daily carried up into the atmosphere in the form of vapour, in which state it occupies a space 1400 times greater than in its ordinary liquid state. It has been found, by experiment, that an acre of ground, in the course of twelve hours of a summer's day, dispersed into the air, by evaporation, 16,000 gallons of water. Every hour there are exhaled in this way, from the surface of the ocean, many millions of gallons, and every year about 40,000 cubical miles of water. This vast body of water, sometimes in an invisible form, and sometimes in the shape of clouds, is carried by the winds over the different regions of sea and land. A part of this water is condensed into thick clouds, and falls down in rains on the continents and Such are the wonderful processes in refer- islands, to fertilize the soil; a part descends ence to respiration as dependent on the atmo- on the seas and oceans; and another part sphere. When we reflect that a stratum of supplies the sources of the rivers, by which it blood, several hundred feet in surface, is ex- is again returned to the ocean, whence it was posed to a stratum of air still more extensive, chiefly derived. This continued circulation and all compressed within the compass of a of vapour through the atmospherical regions, few inches, we cannot but be filled with ad- is one of the most important processes in the miration at the Divine wisdom displayed in system of nature connected with our globe. this and many other functions of the human By means of it, the Creator displays his wissystem, which so far surpass all the contriv- dom and unbounded benevolence, in conveyances of genius, science, and art. In every ing fertility to the different climates of the part of the workmanship of the Almighty, earth, and thus supplying nourishment and even the most minute, we perceive the impress comfort to man and to all the inferior orders of infinite goodness and intelligence, demonstrating that He who formed the human frame and the surrounding elements is "wonderful in counsel, and excellent in working." Not only are terrestrial animals and the fowls of heaven dependent for existence on the atmosphere, but even the fishes of the sea cannot subsist for any length of time without its invigorating influence. Every fish is furnished with an air-bladder, by which it is enabled to rise in the water, or sink into it at pleasure. The lungs of fishes are their gills; these consist of filaments arranged somewhat like the feathers of a quill; they are found to be covered with minute processes, crowded close together, and on which are observed, by the microscope, millions of capillary blood-vessels spread, like a net-work, over the 6. The density of the atmosphere gives whole surface. It is through the thin coats buoyancy to the clouds, and enables the feaof these vessels that the air acts upon the thered songsters to transport themselves with blood they contain. When a fish is taken ease from one part of the earth to another. out of the water the reason it cannot breathe If the air near the earth were much rarer than is, that these filaments collapse, and adhere it is, the clouds would sink to the surface of together in a mass, and the air cannot separate them. If the air be extracted from the water in which fishes swim, or if they have

of animated existence. But it is evident that, without the ministration of the atmosphere, these beneficent operations could not be carried on, and the earth would be left to parch under the rays of the sun, till it were transformed into a bleak and barren desert. It is owing to this process of evaporation that our clothes and linens are dried, after having been washed, and that our roads are rendered clean for walking upon, after having been drenched with heavy showers of rain, or covered with deep snows; without the operation of which, a thousand discomforts and inconveniences would be felt in all the scenes of domestic life, and the operations of art; and this world would cease to be an abode of happiness and enjoyment.

the earth, involve the world in a dismal gloom, and intercept our views of the beauties of the terrestrial landscape, and of the glories of the

midnight sky. The birds would be unable to light of the stars; while, in another part, the perch on the tops of lofty trees, or to wing soil would be parched, and the grass burned their flight from shore to shore. As a proof up, for the want of a veil of clouds to modify of this, Mr. Robertson, who ascended in a the heat of the sun. One region would be balloon from St. Petersburg, in 1804, informs scorched for want of moisture, and another us that he took along with him some live drenched with excessive rains. The putrid pigeons, and, at different heights, gave liberty exhalations of dunghills, marshes, and poputo these birds, who seemed very unwilling to ac- lous cities, would remain perpetually suspendcept of it. The poor animals were so terri- ed around the places whence they arose, and fied with their situation, that they clung to produce diseases and pestilence, which would the boat of the balloon till they were forced sweep the inhabitants of the earth in rapid from it, when it appeared their fears were succession to the grave. But in the existing not groundless; for their wings were nearly economy of nature, all such disastrous effects useless, from the rarity of the air, and they are prevented by the agency of the winds, fell towards the earth with great rapidity. which distribute the clouds in due proportion The second struggled with eagerness to regain over every land, and serve as ventilators to all the balloon, but in vain; and the third, thrown the regions of the atmosphere. out at the greatest elevation, fell towards the earth like a stone, so that he supposed it did not reach the earth alive. This was evidently owing to the extreme rarity of the air in those upper regions to which the balloon ascended.

8. Air is the vehicle of smells, by the transportation of which we become acquainted with the good or bad qualities of the food which is set before us, and are warned against sitting in places that are damp and dangerous, or entering houses that are unwholesome or 7. The atmosphere is the region in which infectious. By means of the air, the odorifwinds are produced, which perform many im- erous effluvia of plants and flowers are diffused portant offices in the economy of our globe. over the fields, and conveyed to the nostrils, Winds are nothing else than portions of air to increase our delightful sensations, when in motion; and although they sometimes ex- wandering among the scenes of nature. cite our fears by the violence of their rage, 9. Air is likewise the medium of sounds. and scatter destruction by sea and land; yet In consequence of its elasticity and undulattheir agency, on the whole, is highly benefi- ing motion, it conveys to us knowledge and cial, and even essentially necessary to man- enjoyment of different kinds, which cannot be kind. They purify the air by keeping it in conveyed to the organs of sight, of taste, or perpetual motion; they disperse the noxious of smell. A few strokes on a large bell will, vapours that are continually rising from stag- in the course of a few seconds, by the undu nant marshes and common sewers; they lation of the atmosphere, reach the ears of a sweep the chambers of the atmosphere; they hundred thousand men, and convey intimaventilate the streets of populous cities, and tions either of joy or terror. The sounds proprevent the accumulation of those noxious duced by the undulations of the air may be affluvia which would produce pestilence and considered as so many couriers running backdeath; they scatter the seeds of various plants wards and forwards, and in every direction, over every region; they fan the air under the to warn us of danger, to inspire us with joy, scorching heats of summer, and diffuse re- and to communicate various delightful sensafreshment over a fainting world; they make tions. When we walk along the road, musour millstones revolve as nimbly as the wheels ing, and unapprehensive of danger, a mailof a chariot, and they serve as wings to our floating edifices, to impel them across the ocean, and to bring them back laden with the treasures of distant lands.

coach may be whirling on in its rapid career, and just at our heels, ready to roll over us; but the air, like a watchful friend, despatches a courier from a considerable distance to warn Were the agitation to cease which the wind us that danger is approaching, and to remove produces, all nature would be thrown into the to the path of safety. While we walk along utmost confusion. Navigation to distant the streets of London, and other cities, we are shores, as hitherto most generally conducted, continually in danger of cabs, coaches, drays, would be at a stand, and ships would be ar- and other vehicles, rolling upon us; and were rested in the midst of the ocean. The vapours it not that the air, by its undulations, gives us exhaled by the heat of the sun would remain timely notice of their appproach, the accidents for ever fixed over those particular spots from this cause which occasionally occur, whence they arose, instead of being dispersed, would be much more numerous than they as they now are, over every region. One part now are. To this property of the air, we of the world, by the interposition of stationa- owe all the advantages we derive from hearing. ry clouds, would be for ever deprived of the sermons and lectures, and all the pleasures we direct influence of the solar rays, and of the enjoy from friendly and instructive conversa

tion. By means of the tongue and the lips he had only broken a stick or a staff; but after we form articulate sounds, which, by the pre- a little time there was a murmuring for a while vious consent of mankind, become the signs which filled the valleys and woods below. of certain ideas; these sounds are conveyed Descending to the lower valleys and the to the ears of our friends, and inform them of rugged rocks, he fired again, which made a the thoughts and ideas that were previously dreadful sound, as if great guns had been passing through our minds, and their un- discharged, and as if the whole mountain derstandings and hearts becoine impressed had begun to tumble about his ears. The with the same sentiments. Without the min- sound lasted for half a quarter of an hour, till istration of the atmosphere in such cases, all it had reached the most secret caverns, where would be sullen and unmeaning listlessness the sound was enlarged and reflected back in and silence, as in the intercourse of the deaf every direction. These facts show that the and dumb. So that the air may be considered elasticity of the air, which is always greatest as the cement of society-the medium of com- where the air is densest, is essential to the munication between one mind and another, propagation of sound. and the interpreter of the thoughts and purposes of mankind.

10. The atmosphere is the cause of that splendour and universal light around us, To the same cause, we are indebted for all which lays open to our view the landscape the pleasures and harmonies of music. Music of the world. Were this atmosphere deis one of the purest and most refined of our stroyed, we might see the sun without enjoysensitive pleasures. It possesses the power ing the light and brilliancy of day. That of charming our ears, soothing our passions, luminary would, indeed, strike our eyes with and affecting our hearts; it dissipates the a vivid brightness when we turned round to gloom of melancholy, animates the vital spirits, behold his flaming orb; but it would appear and gives sublimity to our thoughts and senti- only as a blazing fire during night, in a spaments. When a lady tunes her melodious cious plain, where all is gloom and darkness voice, or touches with her fingers the keys of around. It would suddenly burst on our view the piano-forte, or the strings of the lyre, the in the eastern horizon, in the morning, and air distributes every musical variation and would not change its aspect in the least, every note, with the utmost precision. It during its course through the heavens, till ̄it conveys its message with the greatest impar- suddenly disappeared in the western sky. tiality to the ear of every listener. Though many instruments may be employed, and a thousand persons be present, and placed in every direction, it distributes the harmony alike to every ear. It keeps the most exact time-it conveys the slightest inflections of the voice, and the smallest variation of a tone. It runs through the whole compass of music, swells the sounds, and makes them even thunder in our ears. The next moment, it makes them flutter and melt into dying strains, After this, it swells the notes again, and sinks them in their turns. Thus it expresses, in the most lovely manner, every passion and emotion of the soul, and charms every heart with its persuasive sounds.

The objects immediately around us would be partially visible; but the rays of the sun which fell on distant objects would be for ever lost in the expanse of the heavens; and when we turned our back to the sun, nothing would present itself but an abyss of darkness, and the whole horizon involved in a dismal gloom. The number of objects in the beavens would, indeed, be augmented, for the stars would shine through a canopy as black as ebony, even when the sun was above the horizon; but all the gay colouring of the terrestrial landscape, which now delights the eye and the imagination, would be for ever veiled from the inhabitants of the world. In such a state of things, it would be always night; and the difference between such a night and that which we now enjoy, would be, that the celestial orbs, instead of being grounded on a beautiful azure sky, would appear on a black canopy, like so many white points on a dismal mourning carpet,

That all the effects now stated are owing to the ministration of the atmosphere, is proved by one decisive experiment. Place a small bell under the receiver of an air-pump; let it be rung, and the sound will be heard at a considerable distance. Exhaust the air from the receiver, and the sound can scarcely But the Almighty, whose arrangements be heard by the nicest ear. Even in places have all a respect to the happiness of his where the air is not excluded, but only highly creatures, has enveloped our globe with an rarefied, as in the higher regions of the atmo- atmosphere, and has endowed it with a capasphere, sounds are scarcely heard. Fredli- city of reflecting and refracting the rays of chius, a gentleman of Hungary, informs us, light in all directions. This atmosphere, too, that when he was on one of the loftiest tops is charged with innumerable myriads of wa of the Carpathian mountains, he fired a pistol, tery particles, exhaled by evaporation from which at first made no greater noise than if every region of the sea and land. In the