SHELLS CONNECT ORGANIC AND INORGANIC BEINGS.

created beings, is frequently far beyond the reach of human observation; yet, from a knowledge of some cases, we have reason to suppose that such a link. exists in all. The point at which inorganic matter stops, and from which organized nature commences, is, it may be, the shells of snails and other animals, which increase with the living creatures that inhabit them for these shells seem to partake of the nature of both organic and inorganic matter. They are of a remarkably firm texture; and some of them are exceedingly strong and impenetrable. They form a sort of coat of mail to the animals which wear them, admirably adapted to resist the dangers to which they are commonly exposed.

Though it is difficult to determine to which class. of objects shells belong, yet the investigation of the most patient and skilful naturalists has determined them to belong to the class of organized bodies. M. Herissant, in the Memoirs of the Academy of Sciences for 1766, has discovered the structure of shells to be organical. In the numerous experiments that he made on an immense number, and a very great variety of animal shells, he constantly found that they were composed of two distinct substances; one of which is a cretaceous or earthy matter; and the other appeared, from many experiments made upon it by burning, distillation, and otherwise, to be evidently of an animal or membraneous nature, which (after he had separated the earthy matter from it)

STRUCTURE of shelLS—THEIR COLOURS.

exhibited satisfactory proofs of a vascular and organical structure. He shows that this membraneous

substance is an appendage to the body of the animal, or a continuation of the tendinous fibres that compose the ligaments by which it is fixed to its shell; and that this last owes its hardness to the earthy particles conveyed through the vessels of the animal, which fix themselves into, and incrust, as it were, the meshes formed by the reticular or net-like filaments of which this membraneous substance is composed. On the occasion of the colours of different shells he remarks, that Nature, always magnificent in her designs, but singularly frugal in the execution of them, produces these brilliant decorations at a very small expense. The membraneous substance above-mentioned is plaited and rumpled in such a manner, that its exterior lamina, incrusted with their earthy and semi-transparent matter, form an infinite number of little prisms, placed in all directions, which refract the rays of light, and produce all the changes of colour observable in shells." These, I conceive, constitute the lowest order of organized bodies, and the first above mere rude matter.

STRUCTURE OF VEGETABLES.

THE STRUCTURE OF VEGETABLES.

VEGETABLE substances, in which organization appears more evident and perfect, are the next I shall mention. Here organization is unquestionable, and bears a sort of analogy to that of animals. It is not, however, my intention to describe the nature and construction of different plants and vegetable productions at large-this is the province of the Botanist; but those functions only which are common to all, or nearly all, and which appear essential to vegetation. To excite an interest in the mind on this subject, let it be recollected, that this order of productions is of the greatest moment to ANIMALS of all descriptions, rational as well as irrational; as it constitutes either their immediate food in its vegetable form, or indirectly, by affording food to the animals on which they feed. Were, therefore, the vegetable creation to be annihilated, or, which would amount to the same thing, were the organization of vegetables to be destroyed, their species would cease to be propagated, and the whole animal creation must ultimately perish. In order to unfold the wisdom of God in this part of creation, we must consider

CONSTITUTION OF VEGETABLES.

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The constituent Principles of Vegetables; their neral Structure, and its Suitableness to the process of Vegetation; and the Functions with which they are endowed for the Propagation of their Species.

THE CONSTITUENT PRINCIPLES OF VEGETABLES.

First. We must consider THE CONSTITUENT PRINCIPLES of vegetables, or the materials of which they are composed. As they are principally designed for the food and support of animals, it is rational to expect that, being formed under the immediate eye of infinite Intelligence, they will be found, on investigation, to contain those essential ingredients which are adapted to these purposes. For though it be the design of the beneficent Creator to adorn the surface of the earth, and afford a pleasing gratification to the senses of man, yet these objects are manifestly subservient to immediate utility: and a close attention to a chemical analysis of vegetable substances shows that they are perfectly adapted to their design, and that they contain whatever is necessary to the support of animal life.

The substances at present known to chemists, which they have not hitherto been able to decompose, amount to forty-eight: many of these exist in plants;

CONSTITUTION OF VEGETABLES.

the rest belong, exclusively, to the mineral kingdom; for it is a fact, that no substance (we mean simple substance) has been yet found in the animal kingdom which does not exist also in vegetables."

Sir Humphry Davy enumerates the following compound substances found in vegetables :-gum, or mucilage, and its different modifications; starch, sugar, albumen, gluten, gum elastic, extract, tannin, indigo, narcotic principle, bitter principle, wax, rosins, camphor, fixed oils, volatile oils, woody fibre, acids, alkalies, earths, metallic oxides, and saline compounds.

By analyzing each of these products, we come at last to those bodies which we are at present obliged to consider as simple, because they have not yet been decomposed, and of which, accordingly, we must suppose that vegetables are really formed.

Nearly the whole of vegetable substances are composed of four ingredients; namely, carbon, hydrogen, oxygen, and azot. Of these, azot forms but a small proportion even of those vegetable substances of which it is a constituent part, while into many it does not enter at all: so that, upon the whole, by far the greater part of vegetable substances is composed of carbon, hydrogen, and oxygen. We do not mention caloric and light, concerning the nature of which