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would produce an effect similar to that of a heavy wall, or the roof of a house falling flat upon us, and would infallibly drive the breath from our lungs, and crush to pieces every bone. What is it, then, which prevents such a terrible effect? A small quantity of air within us, which would not weigh above a single ounce, by its strong elastic force, counterpoises the effects of this tremendous pressure; so that, instead of lying as a mountain on our loins, it acts like wings to our feet, or like sinews to our limbs. When a flat bottle is empty, and laid on its side, we might imagine that the weight of the air would break it to pieces; but the air which is contained within the bottle, whether stopped or not, has the same power by its elasticity, to prevent its breaking, as the air without has to crush it to atoms. But, if we apply a syringe to the neck of such a flat bottle, and exhaust the air which is inclosed within, the extraction of that small body of air, which, by its elastic spring, supported the sides of it, gives room to the external air to act on the surface of the bottle with all its force, and the bottle will fly into a thousand pieces. Such would be the case with respect to our own bodies, if an exact balance were not kept up between the pressure of the atmosphere without, and the elastic force of the air within; and, in this instance, as well as in a thousand other instances, we have a striking evidence both of the wisdom and the benevolence of Him who at first created and arranged all the

powers and elements of nature, so as to render them subservient to the preservation and comfort of every species of animated existence.

It is owing to the same admirable arrangement of the Creator, that our dwellings are not crushed to atoms. Suppose an apartment only twelve feet square, and nine feet high, the pressure of the air upon the four sides, and the roof, containing five hundred and seventy-six square feet, is equal to one million, two hundred and forty-four thousand, one hundred and sixty pounds! This enormous pressure is balanced by the resistance of the small quantity of- the air in the room, which weighs only ninety-seven pounds; so that, here is a small weight of ninety-seven pounds, counteracting a pressure of 1,244,160 pounds! Without this wonderful balance, no house could be habitable, no creature could remain alive; our glass windows would be shattered to atoms; an armytent, a peasant's house, or a shepherd's hut, yea, even our most stately edifices, would be crushed to atoms.

It appears, then, that we are immersed in an invisible fluid, which, on the one hand, by its enormous pressure, threatens to crush us to the earth, and, on the other, by its elastic force, to burst our blood-vessels, and tear our whole frame to pieces. The equality or equipoise of these two formidable and death - menacing powers, is our only safeguard and defence ; and shows vis how "fearfully and wonderfully" we are every moment preserved by that Almighty Being, "in whose hand our breath is, and whose are all our ways." Here we have a striking evidence of his benevolence and skill, in having, by his wisdom, reconciled and balanced two such formidable and contending powers, and so tempered them, that the impetuosity of the one is checked by the activity of the other; and all nature, instead of being shattered and destroyed, is preserved in safe and harmonious order. Were it his design to destroy the inhabitants of our world, or to render them miserable, we see how easily this could be effected. He has only to permit one of those powers . now described to act without control, and the work of destruction is at once accomplished. So that in his "hand is the soul of every living thing, and the breath of all mankind." He upholdeth our souls in life, and his merciful visitation sustains our spirits. It is the province of true philosophy to trace the attributes of the Almighty, in every part of his operations, in the system of nature; and there is no scene throughout the universe, where his voice is not heard, and where his power and wisdom are not conspicuously displayed to those who have ears to hear, and eyes to see, and spiritual discernment to recognise the footsteps and the agency of an almighty, though invisible, Intelligence; "for in him we live, and move, and have our being."

CHAPTER IV.

The elasticity of the air, and the phenomena it explains.

The atmosphere is that ocean of air which surrounds our globe on all sides, and in which we live and breathe. We are plunged into the bottom of this vast aerial sea, as the fishes are plunged into the depths of the ocean. Before we were brought into the world, we were furnished with a diaphragm and lungs, with cartilages, ribs, and muscles, to enable us to draw in this vital fluid. The first rush of the air into the lungs, and the cries which accompany it, announce life and sensation. More than a hundred muscles are employed in drawing in and expelling this aerial fluid; and this operation is continued, without intermission, till death. In this element we pass the whole of our existence, from the cradle to the grave; it surrounds us wherever we go, whether on sea or land, and almost all our enjoyments depend on its benign agencies. This element, however, is impalpable to our senses. By its transparency, it escapes our ocular inspection; by its thinness, it eludes our grasp; it cannot be perceived by our smell or taste, nor even by our organs of hearing, unless when it is in a state of tremor and agitation. But we are fully assured, in numerous instances, that the powers of nature may be in complete existence, though they are imperceptible to every organ of sensation; and hence we ought to guard against an error common both to the vulgar and to philosophers, that "the things which we cannot see, have no real existence." The atmosphere, though invisible, is one of the most important and essential constituents of our terrestrial habitation. We could live for a few days without food, or drink, or sleep; we could pass weeks and months without the light of the sun, or the glimmering of a star; but if we are deprived only for a few minutes of the vital air, the lungs refuse to play, the heart ceases to beat, the blood stagnates in the arteries and veins; we faint, we sicken, and die. The powers of the animal machine are broken; the thoughts and perceptions vanish; the dust returns to its kindred dust, and the spirit returns to God who gave it.

We shall now chiefly attend to the illustration of the elasticity of the atmosphere. By the elasticity of the air, is meant that property by which it contracts itself into less space, when an additional pressure is laid upon it, and by which it recovers its former dimensions when the pressure is removed. When I take a piece of whalebone, or a watch-spring, and bring the two ends together, as soon as the force thus employed is removed, the spring

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