universal solidifying constituent of all organized compounds. It is the foundation of the living structures; the solid nucleus around which these etherial airs are clustered and condensed in the crucible of the leaf.

And is this the narrow basis upon which the host of living substances is built up? Four elements? each with a definite, unbending set of characters? Is this chemical harmony, to which I have before alluded, produced with so few notes, and without either flats or sharps? Certainly not! The foundations of life-changes are widened, and the materials made plastic and pliant, by the introduction of the principle of allotropism. This very carbon, so indurated, and inflexible and unyielding; which refuses even to melt, and is the very hardest element known, has yet a variety of allotropic disguises, and plays quite a diversity of characters in the chemical drama. Thus we have ordinary wood-charcoal; we have plumbago, or graphite; anthracite ; bright, metallic-looking gascarbon, left in the retorts after distillation of coal; and lamp-black. These are all distinctly-marked forms of carbon; separated farther from each other than many metals, and varying in their relation to heat, electricity, and chemical and molecular forces. But think you that these sooty physiognomies, these Ethiop masks, are to be accepted for what they ap pear to be taken, as indicating any real blackness of nature within? By no means. The poor, despised, colored family may yet emerge transformed into angels of light. And so our shrouded and muffled friend, king coal, or whoever he may be, drops his ebony vestures and bursts upon us, prince of gems,

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the brilliant and incomparable diamond, another of the forms of carbon. What different, relations to light! While the dull, dead charcoal swallows up and almost extinguishes the ray, the flashing crystal scatters the luminous splendors in all directions. And their relations to heat, also, for while the diamond is highly incombustible, and can hardly be made to burn in pure oxygen gas, at a white heat, lampblack, on the other hand, is so combustible, that it may take fire spontaneously in the open air.

This difference of combustibility is a difference of chemical relation to oxygen gas. But of oxygen itself, the all-encompassing, all-determining spirit of the air, what shall I say? This, too, has its double condition, its allotropic mask. Those who are familiar with electrical experiments, will remember the odor which arises during the operation, and which has been termed the electrical odor. Professor Shonbein, a few years ago, set himself to elucidate the cause of this peculiar smell. He found it due to a substance which was generated by the electric discharge, and which he named, from the circumstance of its odor, And what is ozone? Why only another phase an allotropic form of oxygen gas; it is oxygen endowed with new and exalted attributes. Ozone may be produced not only by electricity, but in various ways. If we place a clean piece of phosphorus in the bottom of a glass jar, and partially cover it with water, ozone is immediately generated in the jar, as may be shown by the appropriate tests. Or if we place a little ether in an open jar, and then introduce into it a moderately heated glass rod, ozone

ozone.

promptly appears. On the other hand, heat destroys it. If we pass ozonized air through a red-hot tube, it emerges de-ozonized the properties are lost. It is generated continually in the atmosphere; we cannot tell how, but probably in various ways; chiefly, perhaps, by electrical changes. Late researches, favor the idea that leaves have the power of generating it. It prevails during storms of rain and snow; and its formation appears to be promoted by a moist atmosphere. It may be for this reason that winds blowing from over the sea contain more of it than those which sweep large tracts of land. Ozone is oxygen greatly intensified in its activity; it becomes armed with a new energy, and capable of performing chemical exploits, which, in its other and ordinary state are impossible. It decomposes compounds which, before, it could not disturb. It corrodes and oxidizes metals upon which before it could not act - for example, silver. It quickly bleaches out colors, which were comparatively permanent in the air. It de-odorizes tainted flesh, destroying the effluvium instantly. It carries woody fibre in a short time through a course of decomposition which, with common oxygen, would require years. Generated on a great scale, when we consider the entire atmosphere, it undoubtedly subserves a high purpose in the economy of the globe as a purifier of the air, and a hastener of decay and destructive changes. It has been attempted to connect its presence in the air with the prevalence of epidemics; and though such a relation is eminently possible, it has not, as yet, been satisfactorily traced.

Now we are not for a moment permitted to doubt that the elements carry their properties with them into the organism, and produce effects there in accordance with these properties. This mysterious allotropic plasticity was conferred upon them for real purposes; it is not an aimless caprice of nature, and we cannot explain the facts of the living system, without taking it into account. Oxygen is carried in the torrent of the circulation to all the regions of the body, destroying the textures in its consuming course, but not indiscriminately. While some parts are abandoned to its action, others are saved. That which is ready is seized, that which is not yet ready, remains unacted upon. A selective power is exercised; some are taken, and others left. Now we can clearly understand how this may be, by remembering that the basal carbon of the tissues has its five-fold phases of action; vibrating from the spontaneously combustible lamp-black, to the almost incombustible diamond; and assuming a series of intermediate forms of variable activity. The oxygen itself has also its double or active and passive state, and may be instantly exhaled to an extraordinary intensity of effect. That the elements do thus revolve through the allotropic circles, and take on their various phases in the reactions of the system, is placed beyond question, by several considerations. First, it explains phenomena which are otherwise inexplicable. Second, we know, demonstrably, that an element in one allotropic state may enter a compound, and give it one character, and it may enter it in another state, and give it another character. Third, the elements are changed

in their allotropic forms by the imponderable forces; and these forces, heat, affinity, electricity, and magnetism, are in constant play in the living system. The conditions of change are all there, its necessity is there; and the application of the idea solves many of the old physiological puzzles. Carbon may enter the system in one alimentary compound in the state of lamp-black; in a second, as anthracite; in a third, as diamond; or it may assume these masks under the direction and controlling influence of the nervous system. The bare contact of various substances exalts common oxygen into ozone; and there is no reason to doubt that the conditions by which this change is effected may incessantly occur in the vital domain.

All this is, to me, I confess, very interesting; for it aids to unravel the complex web of our physiological life; it opens to us the ways and means of creative wisdom. But the train of thought we have started carries us to still larger and higher contemplations. The universe, though boundless, is a rational and allconnected scheme; we everywhere touch universal principles, which carry us up to the grand and sublime. In our ordinary restricted range of thought, we regard our earthly home as an independent theatre of being; a world of itself, containing its own springs of action and sources of power, and that the astronomical fire-works of day and night may be, indeed, a very pretty appendage, quite convenient and interesting withal, but hardly of great vital or practical account, a very remote and foreign affair. This is quite a mistake. The dream of astrology was a prediction of science, -the celestial radiations deter