air received by the lungs at one inspiration, only one-fourth part is decomposed at one action of the heart, and this is so decomposed, in the 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 quantities of air and blood which come in contact in twentyfour hours, the air loses three hundred and twenty-eight ounces of oxygen, and the blood, ten ounces of carbon."

Such are the wonderful processes in reference to respiration as dependent on the atmosphere. When we reflect that a stratum of blood, several hundred feet in surface, is exposed to a stratum of air still more extensive, and all compressed within the compass of a few inches, we cannot but be filled with admiration

at the Divine wisdom displayed in this and many other functions of the human system, which so far surpass all the contrivances of genius, science, and art. In every part of the workmanship of the Almighty, even the most minute, we perceive the impress 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 airbladder, 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 whole surface. It is through the thin coats of these vessels that the air acts upon the blood they contain. When a fish is taken out of the water, the reason it cannot breathe is, that these filaments collapse, and adhere 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 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 1,400 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, 1,600 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 islands to fertilize the soil; a part descends on the seas and oceans; and another part supplies the sources of the rivers, by which it is again returned to the ocean, whence it was chiefly derived. This continued circulation of vapour through the atmospherical regions, is one of the most important processes in the system of nature connected with our globe. By means of it, the Creator displays his wisdom and unbounded benevolence, in conveying fertility to the different climates of the earth, and thus supplying nourishment and comfort to man

and to all the inferior orders 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.

6. The density of the atmosphere gives buoyancy to the clouds, and enables the feathered songsters to transport themselves with ease from one part of the earth to another. If the air near the earth were much rarer than it is, the clouds would sink to the surface of 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 perch on the tops of lofty trees, or to wing their flight from shore to shore. As a proof of this, Mr. Robertson, who ascended in a balloon from St. Petersburgh, in 1804, informs us that he took along with him some live pigeons, and, at different heights, gave liberty

to these birds, who seemed very unwilling to accept of it. The poor animals were so terrified with their situation, that they clung to the boat of the balloon till they were forced from it, when it appeared their fears were not groundless; for their wings were nearly useless, from the rarity of the air, and they fell towards the earth with great rapidity. The second struggled with eagerness to regain the balloon, but in vain; and the third, thrown 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.

7. The atmosphere is the region in which winds are produced, which perform many important offices in the economy of our globe. Winds are nothing else than portions of air in motion; and although they sometimes excite our fears by the violence of their rage, and scatter destruction by sea and land; yet their agency, on the whole, is highly beneficial, and even essentially necessary to mankind. They purify the air by keeping it in perpetual motion; they disperse the noxious vapours that are continually rising from stagnant marshes and common sewers; they sweep the chambers of the atmosphere; they ventilate the streets of populous cities, and prevent the accumulation of those noxious effluvia which would produce pestilence and death; they scatter the seeds of various plants over every region; they fan the