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air under the scorching heats of summer, and diffuse refreshment over a fainting world; they make our millstones revolve as nimbly as the wheels of 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.

Were the agitation to cease which the wind produces, all nature would be thrown into the utmost confusion. Navigation to distant shores, as hitherto most generally conducted, would be at a stand, and ships would be arrested in the midst of the ocean. The vapours exhaled by the heat of the sun would remain for ever fixed over those particular spots whence they arose, instead of being dispersed, as they now are, over every region. One part of the world, by the interposition of stationary clouds, would be for ever deprived of the direct influence of the solar rays, and of the light of the stars; while, in another part, the soil would be parched, and the grass burned up, for want of a veil of clouds to modify the heat of the sun. One region would be scorched for want of moisture, and another drenched with excessive rains. The putrid exhalations of dunghills, marshes, and populous cities, would remain perpetually suspended around the places whence they arose, and produce diseases and pestilence, which would sweep the inhabitants of the earth in rapid succession to the grave. But in the existing economy of nature, all such disastrous effects are prevented by the agency of the winds, which distribute the clouds in due proportion over every land, and serve as ventilators to all the regions of the atmosphere.

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 infectious. By means of the air, the odoriferous effluvia of plants and flowers are diffused over the fields, and conveyed to the nostrils, to increase our delightful sensations, when wandering among the scenes of nature.

9. Air is likewise the medium of sounds. In consequence of its elasticity and undulating motion, it conveys to us knowledge and enjoyment of different kinds, which cannot be conveyed to the organs of sight, of taste, or of smell. A few strokes on a large bell will, in the course of a few seconds, by the undulation of the atmosphere, reach the ears of a hundred thousand men, and convey intimations either of joy or of terror. The sounds produced by the undulations of the air may be considered as so many couriers running backwards and forwards, and in every direction, to warn us of danger, to inspire us with joy, and to communicate various delightful sensations. When we walk along the road, musing, and unapprehensive of danger, a mailcoach may be whirling on its rapid career, and just at our heels, ready to roll over us; but the air,

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like a watchful friend, despatches a courier from a considerable distance to warn us that danger is approaching, and to remove to the path of safety. While we walk along the streets of London, and other cities, we are continually in danger of cabs, coaches, drays, and other vehicles, rolling upon us; and were it not that the air, by its undulations, gives us timely notice of their approach, the accidents from this cause which occasionally occur, would be much more numerous than they now are. To this property of the air, we owe all the advantages we derive from hearing sermons and lectures, and all the pleasures we enjoy from friendly and instructive conversation. By means of the tongue and the lips we form articulate sounds, which, by the previous consent of mankind, become the signs of certain ideas; these sounds are conveyed to the ears of our friends, and inform them of the thoughts and ideas that were previously passing through our minds, and their understandings and hearts become impressed with the same sentiments. Without the ministration of the atmosphere in such cases, all would be sullen and unmeaning listlessness and silence, as in the intercourse of the deaf and dumb. So that the air may be considered as the cement of society—the medium of communication between one mind and another, and the interpreter of the thoughts and purposes of mankind.

To the same cause, we are indebted for all the pleasures and harmonies of music. Music is one of the purest and most refined of our sensitive pleasures. It possesses the power of charming our ears, soothing our passions, and affecting our hearts; it dissipates the gloom of melancholy, animates the vital spirits, and gives sublimity to our thoughts and sentiments. When a lady tunes her melodious voice, or touches with her fingers the keys of the pianoforte, or the strings of the lyre, the air distributes every musical variation and every note, with the utmost precision. It conveys its message with the greatest impartiality 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.

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 be heard by the nicest ear. Even in places where the air is not excluded, but only highly rarefied, as in the higher regions of the atmosphere, sounds are scarcely heard. Fredlichius, a gentleman of Hungary, informs us, that when he was on one of the loftiest tops of the Carpathian mountains, he iired a pistol, which at first made no greater noise than if he had only broken a stick or a staff; but after a little time there was a murmuring for a while which filled the valleys and woods below. Descending to the lower valleys and the rugged rocks, he fired again, which made a dreadful sound, as if great guns had been discharged, and as if the whole mountain had begun to tumble about his ears. The sound lasted for half a quarter of an hour, till it had reached the most secret caverns, where the sound was enlarged and reflected back in every direction. These facts show that the elasticity of the air, which is always greatest where the air is densest, is essential to the propagation of sound.

10. The atmosphere is the cause of that splendour and universal light around us, which lays open to our view the landscape of the world. Were this atmosphere destroyed, we might see the sun without enjoying the light and brilliancy of day. That luminary would, indeed, strike our eyes with a vivid brightness when we turned round to behold his flaming orb; but it would appear only as a blazing

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