minute alge which colour the waters of stagnant pools, though the lowest organic process, involves the double action of accretion and disintegration, and defies the power of science to produce. The meanest and least complex form of life it is beyond man's reach to fashion.*

While the ultimate elements of vitality are profusely furnished in the natural world, vegetables alone have sufficient assimilative power to compose their tissues directly from inorganic matter, the liquid and gassy materials, and the earthy particles, which are but minerals decomposed. Not only so, but no part of an organized being can serve as food to vegetables, until, by the process of putrefaction and decay, it has assumed the form of inorganic matter. It is this capacity which renders vegetable organization the essential base of all other. In the absence of vegetation all animals must be carnivorous, and subsist by mutual destruction, which would soon exterminate their species. For this reason it must necessarily precede animal life. That such has been the fact is abundantly proved by geological research, which, reading the history of buried ages in the rocks, shows us that a period of long duration intervened, after the growth of lichens and ferns in the primitive world, before the lowest order of animals made its appearance upon the earth.

Animal organism, on the contrary, requires for its support and

* I am aware that the English philosopher, Mr. Crosse, supposes himself to have produced insect life, by galvanism, from a soluble glass made of pure black flints and caustic soda, dissolved in distilled water. There is no doubt of the good faith and intelligence of Mr. Crosse. Though not disposed to alter the text, I deem it proper to add this note.

† There is a race of Indians, in Utah and Oregon, who are earth-eaters. They are described in Stansbury's account of the Expedition to the Great Salt Lake, as the very lowest order of human beings. Humboldt mentions that the Otomaas, living on the banks of the Orinoco, who subsist mainly on fish, and are averse to any kind of tillage, are addicted to eating a soft, unctuous clay, which they knead into balls and roast by a weak fire. The balls are moistened again, to prepare them for being eaten. A writer in the Journal of the Royal Agricultural Society of England, (quoted in the Patent Office Report for 1851, page 503,) suggests that dirt is eaten for the purpose of supplying a deficiency of lime in the ordinary food of the tribes, in whom this practice has been observed.

development highly organized atoms. The food of animals, in all circumstances, consists of parts of organisms. While some of them feed directly upon vegetation, others, requiring that matter should have taken on a higher order of life before it can support their own, prey upon other and inferior animals. Having a lower assimilative capacity, it is necessary that their food should have been brought by intermediate agents, into combinations agreeing more nearly with those of their own tissues than even vegetable organization. Without some arrangement and gradation of this character, the higher natures must either perish for lack of food, or consume all their activity in chemical transformations, without reserving any for locomotion or other muscular effort. We may remark here, that with this necessity of overcoming and capturing prey, arises a degree of mental power, enabling the carnivorous animals to devise plans, and to compass by association with their fellows, ends beyond their unassisted power. The spider spins an artful web to catch flies, and wolves hunt their game in packs. The superior functions are everywhere united with less energy in the inferior. Those beings in whom the latter prevail are self-sufficing and independent, but have little reach and power beyond the satisfaction of the low primary wants. As we rise in the scale up to man, the crown and roof of things, we find him, of all, the most dependent, the most prone to association, for which, by the faculty of speech, he is most adapted; and by means of association, though alone the least self-sufficing of all beings, he wins the dominion over Nature and her forces, whether animate or inanimate.

Another distinction between animal and vegetable life is this. The growth and development of vegetables depends upon the elimination of oxygen from the other component parts of their nourishment. They are perpetually exhaling this gas from the surfaces of their leaves into the air. The life of animals exhibits itself in the continual absorption of the oxygen of the air, and its combination with certain component parts of the body. Its office is to generate animal heat by burning the combustible substances of the frame. It combines with the carbon of the food, and in so doing precisely the same quantity of heat is disengaged as if it had been directly burned in the air. The result is carbonic acid gas,

IN MATTER AND, FORCE.IVERSITY

which is thrown out of the lungs and the skin; this is absorbed by the leaves of plants, the carbon separated and incorporated into their substance, and the oxygen again exhaled into the atmosphere, to resume its round of circulation.

Man eats the When it enters

To trace the cycle a little farther-the carbon uniting with water in the plant, forms, among other things, starch, which the sap conveys to the part requiring it. It is found largely in the seeds. Starch exists in wheat to the extent of one half the weight of the grain, and it consists of carbon and water only. wheat, but we find no starch in the human body. our frames it undergoes a chemical change, a slow burning, in fact, in which the carbon of the starch combines with oxygen, forming carbonic acid gas, which, together with the liberated water in the shape of vapour, is thrown out of the human system into the atmosphere, to be again converted in the laboratory of the plant into the starch from which they were derived. Having served our purpose in keeping up the internal warmth upon which animal life depends, the disengaged elements are recomposed by the plants into part of their substance, which when completed again serve as fuel in the animal economy.

The instances we have given, will, so far as relates to their organic constituents, suffice to exemplify the law that animals and vegetables are mutually convertible one into the other, and depend on each other for existence. The interchange of their elements is accomplished through the medium of the atmosphere from which plants derive far the greatest portion of their nutriment.* It is

"Two hundred pounds of earth were dried in an oven, and afterwards put into a large earthen vessel; the earth was then moistened with rainwater, and a willow tree weighing five pounds was planted therein. During the space of five years, the earth was carefily watered with rain-water. The willow grew and flourished; and, to prevent the earth being mixed with fresh earth, blown upon it by the winds, it was covered with a metal plate full of very minute holes, which would exclude everything but air from getting access to the earth below it. After growing in the earth for five years, the tree was removed, and on being weighed, was found to have gained one hundred and sixty-four pounds. And this estimate did not include the weight of the leaves or dead branches which in five years fell from the tree.

found by burning any form of vegetable matter, in a dry state, that the organic part, which is combustible and disappears in the air, is by far the largest. It ordinarily constitutes from ninety to ninetyseven pounds in every hundred. This part of the plant can only have been formed from air at first, if not directly, yet from compounds whose elements were themselves derived from air, existing in the soil, and taken up by the roots. In the language of Professor Draper, in his Chemistry of Plants, "Atmospheric air is the grand receptacle from which all things spring and to which they all return. It is the cradle of vegetable, and the coffin of animal life.”

About one pound in ten, upon an average, of the dry weight of cultivated plants, including their roots, stems, leaves and seeds, is formed of matter which existed as a part of the solid substance of the soil in which the plant grew. Every organ in the stalk, stems, and leaves of a plant has a reticulated framework of inorganic matter, the base of which is either silex or lime. Silex, familiar to us in the various shapes of white sand, flint, and crystal of quartz, constitutes more than sixty per cent. in quantity of the soil, sometimes forming as much as ninety-five per cent. It gives porosity to the soil, in order that water and air may be admitted into its texture. Alumina, the base of clay, on the contrary, renders it compact and retentive. The office of silex in plants is to give strength to the straw of wheat, for example; it serves as the bone of all the grass family. From ninety-three to one hundred and fifty pounds of soluble flint are required to form an acre of wheat.

"Now came the application of the test. Was all this obtained from the earth? It had not sensibly diminished; but, in order to make the experiment conclusive, it was again dried in an oven and put in the balance. Astonishing was the result the earth weighed only two ounces less than it did when the willow was first planted in it! yet the tree had gained one hundred and sixty-four pounds. Manifestly, then, the wood thus gained in the above-mentioned space of time was not obtained from the earth; we are therefore compelled to repeat our question, "where does the wood come from?"

The writer who narrates this experiment concludes that the wood did not come from the water, and therefore must have come from the air. As both air and water are inexhaustible in quantity, it is of no consequence, for the purposes of our reasoning, whether it came from one or both.

It is unnecessary to remark upon the several inorganic constituents, which, combining in different proportions in the various species of vegetation, exist in the soil, and must be replaced if extracted; inasmuch as the absence of any one which enters into the composition of a particular plant, is as fatal to its further growth, as the absence of all. An able chemist has familiarized the notion of the deterioration, when the crop is carried away so as to return nothing to the soil, by informing us that "for every fourteen tons of fodder taken from the soil, there are carried away two casks of potash, two casks of lime, one cask of soda, a carboy of oil of vitriol, a large demijohn of phosphoric acid, and other essential ingredients."

The soil is composed, like the plants, partly of organic and partly of inorganic constituents. The latter, or mineral portion, called the subsoil, is formed by the crumbling and decomposition of the underlying rock, or of other rocks, which have been drifted over it by the action of water, in the early convulsions of Nature, or brought down by the streams in time of freshets from the formations of their upper waters, are deposited in alluvium upon the plains of the low countries. Above the subsoil lies a deposit of mould, resulting from the decay of vegetation and of animal remains. The roots of plants, penetrating through the mould to the subsoil, extract from each the species of nutriment, organic or inorganic, of which it is composed. The object of tillage is to facilitate this process. In the order of Nature, however, and independent of tillage, it is obvious that the plant, in the decay of the leaves and branches which fall from it, and finally of its entire substance, must return to the soil all the solid matter which it had abstracted during its period of growth. If the plant was itself made the food of an animal, the same result followed at one additional remove. During the life of the animal, the soluble material of its food is returned to the earth in its urine, the insoluble in its solid excrements, and, when its life is ended, its carcass goes to repay to the earth all that remains unpaid of its borrowings. If the animal serves as food for another, or for a human being, there is but one step more in the journey to the same destination; for man, too, returns to the soil