urged thousands of adventurers, after the discovery of America, to abandon their European homes, and rush to the new worlds;—which has induced thousands within our own times to leave family and friends, and make long and painful pilgrimages to California and Pike's Peak; and which we see every day, all around us, driving men to the borders of infatuation and madness; - it was nothing else than the love of riches, the passion for wealth. It was the belief in the philosopher's stone, by which all common metals might be transmuted into gold. And why not? Philosophers had taught for two thousand years, that the properties of matter are transferable ; that they may be communicated and taken away, abstracted and restored. Certainly, said they, if these properties of matter are transferable, let us transfer to silver the properties of gold. Somewhere hereabouts is a secret of boundless wealth; let us seek and find it. This idea, the natural fruit of the old speculation, fired the imagination of men, and drove them with an unconquerable energy to the task of exploring the earth in all directions. As Professor Liebig justly remarks, it is impossible for us to conceive an idea so superbly calculated to arouse the mind and faculties of men in ignorant and barbarous ages, as that of the philosopher's stone. It could not be disproved, until nature had been rummaged and ransacked, up and down, over and over, through and through. In order to know that the philosopher's stone did not exist, the earth must be perforated and overhauled in every direction. All known substances, organic and inorganic, must be brought into

contact, observed, examined, tested, experimented upon. The thing, said they, must certainly be possible; the secret is only hidden away somewhere in the recesses of nature, to be discovered as the magnificent reward of zeal and enthusiasm of search.

But the omnipotence of the idea is not even yet fully disclosed. Its miraculous power was not to be easily circumscribed. If the metals may be thus transformed into gold, who should limit the magical power of the transforming agent? Other transmutations may also be accomplished; weakness, pain and disease, into robust and perennial health; the wondrous stone becomes an universal medicine: and even the decrepitude of old age changed to the vigor and fire of youth; it is now the elixir of life. Riches give power; without health there is no enjoyment; and wealth and health take on a new and infinite value, for this transient life is to be replaced by a terrestrial immortality. And here, the possibility of earthly happiness, fullorbed and resplendent, was just within grasp; the heaven of hitherto distant and unutterable longings was to descend and flow into the human soul, and fill it with divine felicity. All this was earnestly, intensely, and most religiously believed.

Such was the locomotive attached to one of the trains of human progress. The track, to be sure, was not laid, nor the line graded, nor yet the route determined, nor the engineer forthcoming to explore it. All was darkness and mystery. Nevertheless, some two or three hundred years after the Christian era, we find the engine in readiness, and steam up, and, animated by the most terrific of all motors,—

human passion kindled to white-hot fury, it starts upon its perilous course. And onward, along plain and valley, through swamps and over mountains, amid rocks and forest, and with many a halt and impulsion, crash and rebound, it makes the long run of fifteen hundred years, emerging at last into the light and glory of our modern civilization.

Nor was there anything absurd in the notion of the transmutation of the metals. They who think it was all mere hallucination, profoundly misread this chapter of history. Nothing was more natural or probable, or tallied more exactly with the knowledge already acquired; and accordingly, it was believed in by all the most learned men who distinguished these ages. And even later yet, when science had become much advanced in several of her great departments, we find the very foremost men in Europe, Leibnitz, Spinoza, Lord Bacon, and Sir Isaac Newton, all believed in the transmutation of metals, and the possibility of making gold. Of the history of alchemy, its extravagances and its sober work, its superstitious nonsense, and its possible reasons, its hope forever deferred, and its numerous and valuable discoveries, I cannot here speak, but only refer to its leading idea, and grand impelling motive. From the vagaries of alchemy sprang the facts of chemistry. Men, working in the direction of an illusive purpose, made new discoveries, which they very naturally did not much prize, but which were yet inexhaustible to the world. The science of chemistry may be regarded as established in its great principles at the close of the last century; and yet up to this time the ancient belief

in the transmutation of the elements was hardly shaken. It was one of the formidable tasks of the epoch I speak of, to explode the old notion, and demonstrate that each element has its fixed and unalterable properties. We can now hardly conceive how intimately this idea was interwoven with universal thought. An Italian philosopher went carefully into the proof that water from melted snows was of the same kind and nature as that from common springs and wells; and Lavosier made a course of public lectures and elaborate experiments, to show that water cannot be transmuted into earth. The doctrine of the fixed identities, and determinate, unchangeable properties of the elements, was formally adopted as the basis of the science by the general acceptance of Dalton's atomic theory at the opening of the present century.

Now, it cannot be said that this doctrine has been exploded, or that the foundations of our science have been subverted; but the progress of inquiry has developed some curious and unexpected things within the last few years, which have not a little startled our philosophers, and made it necessary for them essentially to modify their views of the nature of the elements. For although each is still held to its identity, and forbidden to turn into another element, yet it would almost seem as if they were restless under the restriction, and bound to have compensation by changing among themselves into a variety of conditions, and assuming a marked diversity of phases. We no longer know the elements each by a narrow and rigid set of properties or characters which make

up its personal identity, the true physiognomy is concealed, the personality is obscured, and the changing properties are only successive disguises which hide the real individuality. The classical student reads of strange metamorphoses which took place in the mythical ages. Gods and men were shelled out of their identities, and projected into each others semblances. Men and women were transformed into trees and flowers, beasts and fishes. But none of the wondrous things which happened in those good old times take place now. Smith may not be transformed into Brown, nor Jones into an oak or an antelope. Yet Smith may come before us in a series of characters, so that the stranger would be puzzled to know where the genuine smithhood of the case was to be found. Most of the chemical elements thus take on double or triple states, masquerading from one set of habitudes to another, until we presently begin to wonder if the dreams of the alchemists will not at last be realized. This doubleness, or variety of conditions, which nearly all the elements may assume, is termed allotropism; the term allotropic meaning simply another state. In what it consists we do not know. The word describing it explains nothing; the phenomenon is altogether mysterious. Attention was first called to it by the celebrated Berzelius, of Sweden, and since then discoveries pertaining to it have rapidly multiplied.

In illustration of this matter, let us take the familiar, tangible, solid element, sulphur. We know it in its ordinary form as a yellow, opaque, brittle substance, with a slight, peculiar odor, insoluble in water,