Oxygen, Hydrogen, Carbon, and Nitrogen,--do not turn away from us, gentle reader, we will not be grimly scientific, but a few of the terms of science must be employed, even here,--these four elements are the chief ingredients of all vegetable and animal structures. When separated from their connections, three of them are gases; and the fourth, in union with one of the others, is also a gas. In various combinations they form literally the dust of the earth, they make rock and water, vapor and air. In the hand of the Almighty, they are so many plastic elements, that form now a plant of the lowliest condition, now a magnificent oak, now a fish, and now a man. And the germ of each organized being bequeathes to its offspring the power to reproduce its likeness,--so that each succeeding generation is a repetition of its predecessor. There is no change in plants and animals from the first; the same materials in the same proportions that were selected by the earliest trees for their composition are chosen now; and in form and function the last animal is a precise copy of the first of his race. If we attempt to trace a particle of matter, we shall find its wanderings endless. Annihilation is a term which is not applicable to material things. Matter is never destroyed; it rarely rests. Oxygen, for instance, the most important constituent of our atmosphere, is the combining element of all things, the medium of communication between the kingdoms of Nature, the agent of the interchanges that are continually taking place among all created things. Oxygen keeps life in man, by combining with his blood at every inhalation; it is absorbed by flowers, to be employed in the perfection of the fruit; many minerals are incapable of the various uses of society, until oxygen has attacked and united with them. It gives us lime and soda, the oil of vitriol, and common salt; the mineral pigments in common use are impossible without it; and the beautiful colors of our autumn leaves are due to the combination of oxygen with their juices. It enters into all plans and operations with a helping hand; animals and plants owe their lives to it; but when the shadow of death begins to fall upon them, it is as ready to aid in their destruction. Like calumny, which blackens whatsoever is suspected, oxygen pounces upon the failing and completes their ruin. The processes of fermentation and putrefaction cannot commence in any substance, until it has first taken oxygen into combination. Thus, cans of meat, hermetically sealed, with all the air first carefully expelled, undergo no change so long as the air does not get access to them. If the minutest opening remain, the oxygen of the atmosphere combines with the contents of the can, and fermentation or putrefaction follows. Rust, which takes the keen edge from the knife, is only another name for oxydation: keep the knife bright, and no oxygen dares touch it; but the slightest blemish is made a loophole for the