A knowledge of Aristotle’s works was transferred by Byzantine writers to Egypt; and, when that land was overrun by the Arabs in the seventh century, they adopted his system, spreading it abroad wherever their conquests extended. In the eighth century they carried it into Spain, where it flourished throughout their occupation of that country. From the ninth to the eleventh century the greater part of Europe was in a state of barbarism. The Moslem caliphate in Spain, under the beneficent rule of Jusuf and Jaküb, alone preserved science from extinction. Cordova, Seville, Grenada, and Toledo were the chief seats of learning in Western Europe; and it was mainly through “the perfect and most glorious physicist,” the Moslem Ibn-Roshd—better known as Averroes—(1126–1198), that Christian scholiasts like Roger Bacon acquired their knowledge of the philosophical system of Aristotle, and mainly through the Moslems Geber and Avicenna that they gained acquaintance with the science of the East.

The conception that matter is made up of particles or atoms, and that these particles are in a state of ceaseless motion, is to be met with in Hindu and Phœnician philosophy. It was taught by Anaxagoras, Leukippos, and Demokritos to the Greeks, and by Lucretius to the Romans. Leukippos and Demokritos explained the creation of the world as due solely to physical agencies without the intervention of a creative intelligence. According to their theories, the atoms are variable, not only in size, but in weight. The smallest atoms are also the lightest. Atoms are impenetrable; no two atoms can simultaneously occupy the same place. The collision of the atoms gives them an oscillatory movement, which is communicated to adjacent atoms, and these, in their turn, transmit it to the most distant ones. Anaxagoras taught that every atom is a world in miniature, and that the living body is a congeries of atoms derived from the aliments which sustain it. Plants are living things, endowed like animals with respiratory functions, and, like them, atomically constituted. This philosopher was so far in advance of his age that his countrymen accused him of sacrilege, and he only escaped death by flight. Further, the assumption that these atoms exert mutual attractions and repulsions is probably as old as the fundamental conception itself. At least, so far as can be traced, the conceptions of atoms and atomic motion are indissolubly connected. This is not the place to develop the subsequent history of the doctrine of the atom, nor need we now concern ourselves with the old metaphysical quibble of its divisibility or indivisibility. It may be, as Lucretius said, that the original atom is very far down. It may be that the physical atom is something which is not divided, not something that cannot be divided. This theory, dimly perceived in the mists of antiquity, has grown and strengthened with the ages, and in its modern application to the facts of chemistry has acquired a precision and harmony unimagined even by the poets and thinkers of old. We shall see later how the whole course of the science has been controlled, illumined, and vivified by it. It is not too much to say that the chemistry of to-day is one vast elaboration of this primeval doctrine.

CHAPTER III
Alchemy

Although the intellectual tendencies of the Hellenic mind were hardly calculated to favour the development of chemistry as a science, the speculations of the Greeks concerning the essential nature of matter and the mutual convertibility of the “elements” led incidentally to an extension of the art of operative chemistry. This extension resulted from attempts to realise what was the logical outcome of the teaching of their philosophers—viz., the possibility of the transmutation of metals. The idea of transmutation has its germ in the oldest systems of philosophy. It was a plausible doctrine, not wholly unsupported by the phenomena of the organic world; and it naturally commended itself to men who were only too prone to adopt what their cupidity and love of wealth predisposed them to believe.

It has been assumed that alchemy at no time in its history had the slightest claim to a philosophical foundation, but that its professors and adepts, even at the outset, consciously traded on the credulity and greed of their dupes. Much may be urged against such a partial view. The supposition is not consistent with history or with evolutional tendencies. It may be, as Davy once said, that “analogy is the fruitful parent of error;” but the idea that metals could be modified—could even be changed one into the other—seemed to find support in innumerable chemical phenomena well known but imperfectly understood. The fact that alchemy—that is the profession of making gold from other metals—came to be practised by rogues is no proof that it never had, and never could have had, a philosophical basis.

The changes which substances experience under the influence of fire, air, and water, or as the result of their action on each other, are frequently so profound that even the most superficial of the early observers of chemical processes could not fail to be impressed by them. Many of these changes are, in fact, far more striking as regards alteration in outward characters—such as colour, lustre, density, etc.—than are the differences between individual metals; say, between lead and tin, or between tin and silver, or between brass and gold. That copper ores, by appropriate treatment with other ores, or that copper itself by the addition of another metal, could be made to furnish a metallic-looking substance having certain of the attributes of gold was known to the earliest workers in metals. What is thought to be the oldest chemical treatise in existence is a papyrus in the possession of the University of Leyden. It consists of a number of receipts for the working of metals and alloys, and describes methods of imitating and falsifying the noble metals. It explains how, by means of arsenic, a white colour may be given to certain metals, and how, by the addition of cadmia, copper acquires the colour of gold. The same papyrus describes a method of blackening metals by the use of preparations of sulphur. The limited knowledge of chemical phenomena and of chemical processes which these early workers necessarily possessed, so far from precluding a belief in the possibility of transmutation, actually encouraged it. As nothing was known of the true nature of brass or of its exact relation to copper, it was not unreasonable to suppose that, if this substance could be made to acquire some of the attributes of gold by a process essentially chemical, processes of a like nature might cause it to acquire, if not all, at least so many of them as to enable it to pass for gold of greater or less fineness. To them, as to us, perfection was, in technical practice, a question of degree: the very language of the metallurgists of old was in this respect nowise different from that of the metallurgists of to-day.

It is not necessary to suppose that these early attempts were deliberately and consciously fraudulent, like those of coiners who knowingly seek to make an alloy of lead and tin simulate silver. The first alchemists sought in good faith to make something which should be of the true nature and essence of gold as they conceived it to be. In fact, the idea of transmutation had a rational foundation in a theory of the intrinsic nature of metals which may be looked upon as a development of the ancient beliefs concerning the essential nature of all forms of matter.

Just as the Aristotelian “elements” were qualities which, according to their degree, determined the nature of substances, so, in like manner, the specific character of a metal depended upon the relative proportion of its “sulphur” and “mercury.” These terms had no certain reference to what we to-day understand by sulphur and mercury. They denoted simply qualities. The essence or “element” of mercury conferred lustre, malleability, ductility, and fusibility, or, speaking generally, the properties which we connote as metallic; while to the essence or “element” of sulphur was to be attributed the combustibility—or, speaking generally, the alterability—of the metal by fire. By modifying the relative proportion of these constituent elements, or by purifying them from extraneous substances by the operations of chemistry, it was conceived that the several metals could be changed one into the other. To effect this purification it was necessary to add various preparations known as “medicines,” chief among which was the Great Elixir, or Magisterium, or the Philosopher’s Stone, by which the final transformation into the noblest of the metals could alone be achieved.

The Arabic words kímyâ and iksír were originally synonymous and each was used to denote the agent by which the baser metals could be transmuted into silver and gold. Ultimately the former term became restricted to indicate the art of transmutation (alchemy), whereas iksír, or al-iksír, continued to denote the medium by which the transmutation was effected. By later writers the term was used to indicate a liquid preparation—the quintessence of the philosophers—whence we have the word elixir, which always means a liquid.