During fermentation, the oxygen is absorbed, and carbonic acid is evolved. During putrefaction, oxygen is taken up also. There are many operations, too, connected with the arts, in which that fluid is abstracted from the air. The very soil is constantly acting on the atmosphere, and is, indeed, one vast and extended laboratory, where chemical processes, on a large scale, are going on without interruption. The putrefaction of the animal and vegetable materials, used as manure, is much promoted by free exposure to the air; hence one of the advantages of ploughing the land so universally adopted. The very nature of the soil is greatly altered by that process, and much of that change depends not only on the chemical processes just spoken of, but upon the action of the air itself, on the essential particles of the clod. From the surface of newly turned up soil, it is understood by intelligent agriculturists, that much gaseous or elastic vapour is evolved; and we have heard it observed by intelligent ploughmen, that one of the most delightful things is the air which arises from newly ploughed fields in the morning. It is said that it imparts an invigorating, and wholesome sensation throughout the body, and from thence to the mind. All those processes we referred to, abstract from the atmosphere its most essential part, the oxygen gas. Did that process of abstraction go on without its being counterbalanced by others, imparting that principle to supply the place of that abstracted, then the atmosphere in the course of time would become unfit to support combustion or flame,—unfit to support animal respiration; and the consequence would be, that the surface of the earth would soon be uninhabitable, would soon be a lifeless desert. Such would be the inevitable consequence. But a wise and a good Creator has prevented the occurrence of that catastrophe. He has so ordered it, that one department of nature shall correct the bad tendencies of the other;—he has placed a weight at the opposite end of the balance, to counterpoise and balance the glorious work of his hand. Animal life is met by vegetable life: their results are made to neutralize those of each other, and with a wisdom truly the Father’s, found in his works alone, he has made the apparently hurtful consequence of animal life, the very means for the maintenance of the life of vegetation. The results of the function of respiration so necessary to animals, are highly useful to vegetables. Those products that are hurtful are absorbed by the leaves of plants, which are analogous to our lungs or breathing apparatus, and the oxygen consumed by animals is replaced by the evolution of a large quantity of that principle. During sunshine, plants, especially in water, give out a large quantity of that principle, as may be seen by putting grass leaves into a jar filled with water, and exposing them to sunshine. Bubbles of air soon appear, and collect at the top of the jar; they are oxygen gas.