The Atmosphere. The atmosphere is one of the most essential appendages to the globe we inhabit, and exhibits a most striking proof of Divine skill and omnipotence. It is now ascertained to be a compound substance, formed chiefly of two very different ingredients, termed oxygen and nitrogen gas. Of 100 measures of atmospheric air, 21 are oxygen, and 79 nitrogen. The one, namely, oxygen, is the principle of combustion. It is absolutely necessary for the support of animal life, and is one of most important, substances in nature. The other (nitrogen) is altogether incapable of supporting either flame or animal life. But the term atmosphere is also applied to the whole mass of fluids, consisting of air, vapours, electric fluid, and other matters which surround the earth to a certain height. This mass of fluid matter gravitates to the earth, revolves with it in its diurnal rotation, and is carried along with it in its course round the sun every year. It has been computed to extend about 45 miles above the earth's surface, and it presses on the earth with a force proportioned to its height and density. From experiments made with the barometer it has been ascertained, that it presses with a weight of about 15 pounds on every square inch of the earth's surface; and, therefore, its pressure on the body of a middle-sized man is equal to about 32,000 pounds, or 14 tons avoirdupois, a pressure which would be insupportable, and even fatal, were it not equal on every part, and counterbalanced by the spring of the air within us. The pressure of the whole atmosphere upon the earth is computed to be equivalent to that of a globe of lead 06 miles in diameter; in other words, the whole mass of the air, which surrounds the globe, compresses the earth with a force or power equal to that of five thousand millions of millions of tons. This amazing pressure is, however, essentially necessary for the servation of the present constitution of our globe, and of the animated beings which dwell on its surface. It prevents the heat of the sun from converting water and all other fluids into vapour; and preserves the vessels of all organized beings in due tone and vigour. Were the atmospherical pressure entirely removed, the elastic fluids contained in the finer vessels of men and other animals would inevitably burst them, and lite would become extinct ; and most of the substances on the face of the earth, particularly liquids, would be dissipated into vapour.

Besides these, the atmosphere possesses a great variety of other admirable properties, of which the following maybe mentioned. It is the vehicle of smells, by which we become acquainted with the qualities of the food which is set before us, and learn to avoid those places which are damp, unwholesome, and dangerous. It is the medium of sounds, by means of which knowledge is conveyed to our minds. Its undulations, like so many couriers, run for ever backwards and wards, to convey our thoughts to others and theirs to us, and to bring news of transactions which frequently occur at a consider-able distance. A few- strokes on a large bell, through the ministration of the air, will convey signals of distress, or of joy, in a quarter of a minute, to the population of a city containing a hundred thousand inhabitants. It transmits to our cars all the harmonies of music, and expresses every passion of the soul: it swells the notes of the nightingale, and distributes alike to every ear the pleasures which arise from the harmonious sounds of a concert. It produces the blue colour of the sky. and is the cause of the morning and evening twilight, by its property of bending the rays of light, and reflecting them in all directions. It forms an essential requisite for carrying on all the processes of the vegetable kingdom, and serves for the production of clouds, rain, and dew, which nourish and fertilize the earth. In short, it would be impossible to enumerate all the advantages we derive from this noble appendage to our world. Were the earth divested of its atmosphere, or were only two or three of its properties changed or destroyed, it would be left altogether unfit for the habitation of sentient beings. Were it divested of its undulating quality, we should be deprived of all the advantages of speech and conversation, of all the melody of the feathered songsters, and of all the pleasures of music ; and, like the deaf and dumb, we could have no power of communing our thoughts but by visible signs. Were it deprived of its reflective powers, the sun would appear in one part of the sky of a dazzling brightness, while all around would appear as dark as midnight, and the stars would be visible at noon-day. Were it deprived of its refractive powers, instead of the gradual approach of the day and the night, which we now experience, at sun-rise we should be transported, all at once, from midnight darkness to the splendour of noon-day; and, at sun-set, should make a sudden transition from the splendours of day to all the horrors of midnight, which would bewilder the traveller in his journey, and strike the creation with amazement. In line, were the oxygen of the atmosphere completely extracted, destruction would seize on all tribes of the living world, throughout every region of earth, air, and sea.