Several other copies of the Abbreviatio have the first two lines, but this alone contains the third. In the Chigi manuscript, the place of these verses is occupied by a curious feat of language:—

To whatever period it belongs, the writer’s purpose was doubtless to recall to the mind the four nations over which Frederick II. ruled, and the splendid kingdoms of Sicily, Germany, and Jerusalem which he gathered in one under his imperial power.

In the Laurentian Library there is a valuable manuscript, written during the summer and autumn of 1266, for the monks of Santa Croce.[102] It contains the De Animalibus ad Caesarem; the Abbreviatio Avicennae, and, as a third and concluding article, an independent version of the Liber de Partibus Animalium, corresponding, as has been said, to books xi.-xiv. of the other versions which the volume contains. Bandini, in the printed catalogue of the library, asserts that this third translation, unlike the two which precede it, was made from the Greek. This is probably correct, as it was only the Greek text which treated these four chapters of the Natural History as a distinct work. He further ascribes the version to Michael Scot, relying no doubt on the general composition of the volume, for this particular translation does not seem to contain any direct evidence of authorship. Thus the doubt expressed by Jourdain in this matter[103] is not without reason, though the balance of probability would seem to incline in favour of Bandini’s opinion; for such a volume can scarcely be assumed to have been a mere miscellany without clear evidence that the contents come from more than one author. Taking it for granted then that the De Partibus Animalium came from Scot’s pen, then this is the third form in which his labours on the Natural History of Aristotle appeared.

In any case, however, his chief merit in this department of study belonged to Michael Scot as the exponent of the Arabian naturalists. It is difficult for any one who has not read the books in question to form an adequate idea of their contents, and still more of their style; even from the most careful description. We are made to feel that the task of the translator must have been a very difficult one. There is a concentration combined with great wealth of detail, and withal a constant nimble transition from one subject to another, seemingly remote, under the suggestion of some subtle connection, which result in a style almost baffling to one who sought to reproduce it in his comparatively slow and clumsy Latin.

No greater contrast could be imagined than that which separates such works from those which are the production of our modern writers on the same subject. Nor does this difference depend, as one might suppose, on the fact that a wider field of observation is open to us, and more adequate collections of facts are at our disposal. Rather is it the case that between ancients and moderns, between the eastern and western world, there is an entirely different understanding of the whole subject. A different principle of arrangement is at work, and results in the wide diversity of manner which strikes us as soon as we open the De Animalibus or the Abbreviatio. We find ourselves in the presence of a system of ideas, more or less abstract, which a wealth of facts derived from keen and wide observation of the world of nature is employed to illustrate. There is a finer division than with us. The unit in these works is not the species nor even the individual, but some single part or passion. This the author follows through all he knew of the multitudinous maze of nature, comparing and discerning and recording with a bizarrerie which comes to resemble nothing so much as the fantastic dance of form and colour in a kaleidoscope.

‘Birds,’ says Avicenna,[104] ‘have a way of life that is peculiar to themselves. Those that are long-necked drink by the mouth, then lift their head till the water runs down their neck. The reason of this is that their neck is long and narrow, so that they cannot satisfy their thirst by putting beak in water and straightway drinking. There is, however, a great difference between different birds in their way of drinking, and the mountain hog loveth roots to which his tusk helpeth, wherewith he turneth up the ground and breaketh out the roots. Six days or thereabout are proper for his fattening, wherein he drinketh not for three, and there are some who feed their hogs and yet will not water them for perchance seven days on end. And in their fattening all animals are helped by moderate and gentle exercise, save the hog, who fatteneth lying in the mud, and that mightily, for thereby his pores are shut upon him so that he loseth nothing by evaporation. And the hog will fight with the wolf, and that is his nature, and cows fatten on every windy thing, such as vetches, beans, and barley, and if their horns be anointed with soft wax, straightway, even while still upon the living animal, they become soft, and if the horns of ox or cow be anointed with marrow, oil, or pitch, this easeth them of the pain in their feet after a journey.’

In another place[105] he continues: ‘Some animals have teeth which serve them not save for fighting, and not for the mastication of their food. Such are the hog and the elephant, for the elephant’s tusks are of use to him in this matter as we have said. And there are animals which make no use of their teeth save for eating or fighting, nay, I believe that every animal having teeth will fight with them upon occasion, and some there are whose teeth are sharp and stand well apart, so that they are therewith furnished to tear prey: such is the lion. And those animals that have need to crop their food, as grass and the like, from the ground, have level and regular teeth, and not long tusks or canines, which would hinder them from cropping; and since in some kinds the males are more apt to anger than the females, tusks have been given them that they may defend the females, because these are weaker in themselves and of a worse complexion, and this is true in a general way of all animals, even in those kinds that eat no flesh, and need not their tusks for eating, but only for defence, such as boars, and this is the reason why they have the strength of which we have just spoken. It is the same with the camel, and so we pass to speak of this general truth as it appears with regard to all other means of defence. Hence hath the stag his horn and not the hind; the ram and not the ewe; the he-goat and not his female, and fish which eat not flesh have no need of teeth that are sharp.’

The city where these strange writings were deciphered and translated into Latin, being itself so strange and remote from the ways of modern life, had a certain poetic fitness as the scene where Michael Scot undertook his labours upon the Arabian authors. No passage of all their texts was more bizarre and tortuous than the mass of intricate lanes which formed then, as they form to-day, the thoroughfares of communication in Toledo. No hidden jewel of knowledge and observation could surprise and reward the translator in the midst of his tedious labours with a flash of sudden light and glory more unexpectedly delicious than that felt by the traveller, when, after long wandering in that maze and labyrinth, he finds a wider air; a stronger light beats before him, beckoning, and in a moment he stands in the full sunshine of the plaza mayor, with space to see and light to show the wonders of mind and hand, and all the toil of past ages in the fabric of the great cathedral.

Such as it now stands, the Cathedral of Toledo had not yet begun to rise above ground when Michael Scot had his residence there, but enough of the ancient city remains to show what Toledo must have been like in these early days. The splendid and commanding site, swept about by the waves of the Tagus; the famous bridge of Alcantara; the steep slope of approach crowned by ancient fortifications; and above all the massed and massive houses of the old town, so closely crowded together as hardly to give room for streets that should rather be called lanes; all this, beneath the unchanging sky of the south, recalls sufficiently what must have been the surroundings of Scot’s life during ten laborious years. Even yet, where white-wash peels and stucco fails, strange records of that forgotten past reveal themselves in the walls and on the house fronts: sculptured stones of every age; bas-reliefs, arabesques; windows in the delicate Moorish manner of twin arches, and a central shaft with carved cornices, long built up and forgotten till accident has revealed them.

Here then, perhaps in some house still standing, the scholar come from Sicily made his home. The quiet courtyard is forgotten; the azulejos have disappeared from walls and pavement; the rich wood-work of the ceilings, still bearing dim traces of colour and gold, looks down on the life of another age; even the curious cedar book-chest has crumbled to dust, for all its delicate defence of ironwork spreading away like a spider’s web from hinges and from lock. But the name and the fame endure, and the years which Michael Scot spent in Toledo have left a deep mark upon that and every succeeding age.

CHAPTER IV
THE ALCHEMICAL STUDIES OF SCOT

The Moorish schools of Spain were famous, not only for their researches in natural history, but also for the interest they took in chemistry, then called alchemy: a name which sufficiently indicates the nation which chiefly pursued these studies, and the language that recorded their progress. The practical turn taken by alchemy, as the foundation of a scientific materia medica in minerals, is shown by the writings of Rases. This author, who belonged to the ninth and tenth centuries (860-940), produced a considerable work on medicine in which he devoted special attention to the diseases of children. Under his name appeared several alchemical writings, either his own or the productions of the school which followed his teaching and borrowed his name.

Michael Scot, as we know, had become familiar with the works of Rases while still in Sicily, and thought so highly of the De Medicina as to borrow thence for his treatise on physiognomy no fewer than thirty-one chapters relating to that subject.[106] It is a natural conjecture then which leads us to find in his acquaintance with this author’s writings the starting-point of Scot’s interest both in medicine and in alchemy. Leaving for the present what may hereafter be said of his name and fame as a physician, let us examine the origin and nature of his work as a student of the Arabian chemistry. We have reached what would seem to be the proper moment for such an inquiry. The treatises of Michael Scot on this subject are not dated indeed, but their form shows them to belong to the epoch of his work as a translator. They were therefore probably produced during the period of his residence at Toledo, and as there is a long interval, otherwise unaccounted for, between 1210, when the Abbreviatio Avicenna appeared, and the date of his next publication some seven years later, this blank cannot be better filled than by supposing that it was during these years he found time for the study of alchemy, and for the translation or composition of the writings in that branch of science which still bear his name.

In this, as in almost all his other studies, Michael Scot sat at the feet of Eastern masters. But the Arabians themselves had derived their chemical science, at least in its first principles and primitive processes, from still older peoples. If we are to understand the progress of human thought in this science we must trace it from the beginning, following again that beaten track of tradition by which not physiognomy and alchemy alone, but almost all the secrets of early times, have reached the modern world.

Primitive chemistry was closely connected with the still older art of metallurgy, out of which it arose by a natural process of development. Those who worked with ores soon discovered the secret of alloys, whereby a considerable quantity of baser metal, such as copper, lead or tin, could be added to gold or silver, so as greatly to increase the bulk of the whole without injuring either its appearance or usefulness. The problem of the crown set before Archimedes, and happily solved by that philosopher in the bath, shows how dexterously alloys were used by the Greeks, and what subtle means were necessary for their detection.

M. Berthelot has reminded us[107] that the transmission of receipts for such processes from early times to our own has been naturally and inevitably secured by the unbroken continuity of practice in the arts which gave them birth, and that they thus passed safely from generation to generation, and even spread from the tribes that originated them to other and distant peoples. He cites in support of this observation a papyrus of the third century, preserved at Leyden, which, he says, contains what are substantially the same directions as those of the chief mediæval authorities in such matters: the Mappae Clavicula and the Compositiones ad Tingenda.[108] These receipts are not unnaturally entitled ‘How to make Gold,’ and it is curious to find in them the veritable starting-point of the dreams which made so many a furnace smoke, and so many a crucible glow during the course of centuries, in the vain hope of effecting an actual transmutation of substance.

Thus it was that in the first ages, long before authentic record, in the dimness of early Egyptian history, or of that still more ancient Pelasgic civilisation from which the pyramid-builders learned so much, the germs of this science may already be perceived. Only one source of genuine gold seems then to have been known: the mines of Ophir. This circumstance, by making the supplies of precious metal small and uncertain, mightily encouraged the art which taught men to counterfeit its appearance in a colourable way. How this was done may be judged of by the receipts themselves. The Mappae Clavicula, for instance, has the following: ‘To make gold. Silver, one pound; copper, half-a-pound; gold, a pound; melt, etc.’ Here indeed a considerable proportion of the precious metal itself was required, but there are other receipts which dispense with any such admixture. It is said, for example, that one hundred parts of copper and seventeen of zinc joined in a state of fusion with divers small proportions of magnesia, sal ammoniac, quicklime, and tartar, yield an alloy which is fine in grain and malleable, which may be polished and used in damascening just as if it were the pure gold that it has all the appearance of being. Such then were the receipts which formed the hereditary riches of the mighty clan of the Smiths. It is easy to see how the famous ‘powder of projection,’ so much sought in later times, was, in fact, but the transfiguration of one of these formulae.

When, during the early centuries of the Christian era, the traditions of Greece found a new home in lower Egypt, and especially in Alexandria, they were profoundly influenced by the still more ancient philosophy of the East. We have already remarked this in the case of another science, that of physiognomy, but the same influence may also be traced in the modification it brought to the notions of primitive chemistry. The Chaldæans and Persians had long believed that the heavens influenced the earth, and were capable of producing strange effects in the lower spheres of being.[109] Their wise men considered that an individual connection could be established between the stars and the elements, the planets and the metals. It was in contact with this new doctrine and under its influence that there arose the hope, soon hardening into a settled belief, that the rules of art might be sufficient to effect an actual transmutation of the baser into the nobler metals, of copper into gold, and of tin or lead into silver.

This opinion must have been immensely heightened, and its authority reinforced, by the secrecy with which the receipts for alloying metals were guarded. These were handed down orally from father to son; were not committed to writing till a comparatively late period, and even then remained for the most part the cherished treasures of temple guilds. On the well-known principle of the proverb, ‘Omne ignotum pro magnifico’ this secrecy tended to confirm the impression that, however much had been communicated, more remained untold, to await discovery by the patient and undaunted chemist. The Therapeutæ or Essenes were among the earliest representatives of this new tendency, as appears from the testimony of Josephus,[110] who describes them as not only devoted to ancient writings, but eager to investigate the properties of minerals. The chief object of their inquiries, the maintenance of health by medicines thus derived from the vegetable and mineral kingdoms, is not only an early instance of the connection between chemistry and pharmacy, but is remarkable as the probable starting-point of the search for the elixir of life: that other and nobler dream which so much of the enthusiastic energy of the mediæval alchemists was spent to realise.

The point of connection between these speculations of Eastern philosophy and the practice of the primitive chemistry may with probability be sought in the fire which of necessity played so large a part in the operations of the metal-worker. Fire bore a highly sacred character in the philosophy and religion of the East. This element, it soon came to be thought by those whom Eastern speculation influenced, might be trusted not only to melt, to calcine and to sublime in the vulgar way, but to form the long-sought link of sympathy between the stars of heaven, themselves compact of fire, and the elements of earth, as these were subjected to its piercing and transforming power. In its due employment the suspected connection between the higher and lower worlds would become an accomplished fact. Thus, under the power of the planets, in some favourable hour and fortunate conjunction, the mighty work would be done: the philosopher’s stone discovered, the metals transmuted, and the elixir of life produced.

It is highly curious to find this idea presented in a novel and perhaps an exaggerated form by a writer of the sixteenth century. This was Fra Evangelista Quattrami of Gubbio, semplicista, or master of the still-room, to the Cardinal d’Este. He wrote a book entitled, The true declaration of all the metaphors, similitudes, and riddles of the ancient Alchemical Philosophers, as well among the Chaldeans and Arabians as the Greeks and Latins.[111] According to this work, the potable gold; the elixir of life; the quintessence, and the philosopher’s stone were nothing but fantastic names for the fire itself which was used in distillation and other chemical operations. In this the Frate may possibly have touched the true sense of Al Kindi at least, who, in his commentary on the Meteora,[112] speaks of fire as if it were the all in all of the alchemist.

While the primitive chemical practice followed the progress of the arts which it served, the new theory of alchemy, with the ever-growing tradition of fantastic experiments arising out of it, found different and less direct channels in its descent from ancient to modern times. It has been customary to speak of the Arabs as if that nation had been the chief means of transmitting the knowledge of Greek doctrine to our mediæval scholars, but we now know that there was a previous link in the chain of intellectual succession. This was supplied by the care and industry of the Syrian subjects of the early Caliphs, nor did their learned men play a less important part in the history of chemistry than in that of the other sciences. Sergius of Resaina, a scholar of the fifth century, was, it is said, the first Syrian who attempted to translate the Greek chemists, several of whom mention him by name. The chief development of this work belongs, however, to the ninth and tenth centuries, and its glory must ever remain with the great school of Bagdad. Chemical treatises composed by Democritus and Zosimus[113] were there and then rendered into Syriac, as may be seen by the manuscripts still preserved in the British Museum and at Cambridge.

It was not long before the Arabs themselves began to feel powerfully the intellectual impulse thus communicated to them in the heart of a country which they had made their own. Khaled ben Yezid ibn Moauia, who died in the year 708, is said by their historians to have been the first of that nation who devoted his attention to chemistry. In his case the filiation of doctrine would seem very plain, as he was the pupil of a Syrian monk named Mariannos. Djabar, the Geber of Western writers, followed in the same line of study, and from the ninth century there was a regular school of Arabian chemists whose labours may be studied in the manuscript collections of Paris and Leyden.

In the eleventh century appeared a curious phenomenon, in the shape of a dispute among the Arabians of that day regarding the truth of the tradition which pronounced the transmutation of metals possible. The unwearied but still unavailing experiments which had now been carried on through several ages, produced at last their inevitable effect in the shape of philosophic doubt, eagerly urged on the one part and as eagerly repelled on the other. The chemical school was now divided according to these opposite opinions, and each party in their writings sought to give weight to what they taught by borrowing in support of their arguments the names of the mighty dead. In this conflict it was left to the followers of Rases to sustain the affirmative and to assert the possibility of transmutation. These were the apologists for the past, and the advocates, in the name of their great master, of that hope which had inspired previous research and borne fruit in so many important discoveries.

The defence of the new doubt belonged on the other hand to the school of Al Kindi. This chemist lived and died during the ninth century. He was probably the earliest Arabian commentator on Aristotle, and seems to have paid special attention to the Meteora of that author. The treatise De Mineralibus, so often appended to the Meteora as a supplement, is ascribed to Al Kindi in the Paris manuscript.[114] It represents the alchemy of the time.

Between these two contending parties stood the school of Avicenna, which now occupied an intermediate position and doubted of the doubt. That this had not always been the opinion of Avicenna himself is plain, however, from a passage which occurs in his Sermo de generatione lapidum, where the author unhesitatingly pronounces against the theory of transmutation. ‘Those of the chemical craft,’ he says, ‘know well that no change can be effected in the different species of things, though they can produce the appearance of them: tinging that which is ruddy with yellow till it looks like gold, and that which is white with colour at their pleasure till the same effect is in great measure produced. Nay, they can also remove the impurity from lead, so that it looks like silver, though it be lead still, and can endue it with such strange qualities as to deceive men’s senses, and this by the use of salt and sal ammoniac.’[115] Avicenna was evidently well acquainted with the secrets of art and held them at their proper value. Had his followers in the eleventh century done the same they would have supported the school of Al Kindi instead of taking a less definite position.

This view of the later Arabian schools and their differences is forced upon us by the fact, that works are extant under the names of Rases, Al Kindi, and Avicenna, which evidently belong to the eleventh century, the period when they first appeared, and could not therefore have been written by authors who lived at an earlier date. They are plainly the production of later chemists who followed more or less intelligently the doctrine of these great masters in alchemy. The artifice involved in this ascription of authorship is one which has always been common in Eastern literature.

We have a direct interest in observing that Spain was the country where these developments of the later Arabian chemistry arose, contended and flourished. Spain, therefore, during the eleventh and twelfth centuries, became, by the attraction she offered to European scholars, the country where these theories first reached the Latin races, and began to find an entrance among them. M. Berthelot indeed, by a happy citation, has enabled us to fix, almost with certainty, the very moment of this important event. Robert Castrensis, the author alluded to, remarks: ‘Your Latin world has not as yet learned the doctrine of Alchemy.’ These words are taken from the preface to this author’s version of the Liber de Compositione Alchimiae, and a colophon informs us that the translation was completed on the 11th of February 1182. We may add that the same year, corrected, however, in one copy to 1183, was the date of another of these versions of the Arabian chemistry: that of the treatise called Interrogationes Regis Kalid, et responsiones Morieni.[116] Here then we stand on the threshold of a new age, and find ourselves in presence of an intellectual movement which was certainly of the greatest importance, since in it we may trace the origin of our modern chemistry. The knowledge of what had already been gained by Greek and Arabian alchemists was the first step to independent research among the Latins. The closing years of the twelfth century saw that knowledge at last beginning to unfold itself in a form intelligible to the Western schools.

As in Bagdad during the ninth century, the palmy period of Syrian studies, so in Spain three hundred years later, the work was in its commencement essentially one of interpretation, and the first age of these labours was distinguished by the number of versions which were then produced. From 1182, through the whole of the following century, students laboured in the translation of Moorish books on chemistry. Only towards the close of this period did a tendency become apparent which led in the direction of improvement and innovation. The seed already sown had begun to bear fruit. The material thus derived from Eastern sources was now treated with a new freedom, enriched by the results of original experiment, and edited in forms which betray the influence of scholastic philosophy. The criticism, however, which would determine the precise point when this change began to be operative, and the extent to which it proceeded, attempts what is perhaps an impossible and certainly a difficult task. For it is a remarkable fact that no Arabic texts have been preserved to us which can be regarded as the originals from which these earlier Latin versions were made. This want is probably due to the widespread destruction which overtook the Moorish libraries of Spain.[117] That such originals did at one time exist, however, is made certain by the correspondence which the Latin translations show with those which have come down to us in another language, the Hebrew. The labours of these Latin translators during a hundred years may be found in the manifold collections of chemical treatises, containing some forty or fifty articles apiece, which were arranged and copied out at the beginning of the fourteenth century. These volumes became, after the invention of printing, the chief quarry whence were composed the Ars Aurifera; the Theatrum Chemicum of Zetzner, and the Bibliotheca of Manget.

We are now in a position to understand, not only the nature and progress of the work in which Michael Scot took part, but the exact development which alchemy had reached in his day, and therefore the relation which his chemical publications bore to the general direction of study in this department of science. The time and care which our survey of the field has demanded need not be thought ill spent. It has prepared the way for a more intelligent appreciation of Scot’s labours as a chemist, and has furnished us with the means of coming to a true judgment regarding their authenticity and value.

To put the matter to the proof: we may begin by dismissing altogether from consideration a treatise which has long been attributed to Scot, and still appears in the most recent list of his works: the Quaestio curiosa de natura Solis et Lunae. It has probably received more attention than it deserves since it appeared under Scot’s name in the Theatrum Chemicum.[118] The subject of this treatise is indeed an alchemical one; for the sun and moon of which it speaks are not these heavenly bodies themselves, but, by an allegorical use common in the Middle Ages, and derived from the Eastern theories of sympathy already mentioned, stand for the nobler metals of gold and silver. A brief examination, however, shows that Scot could not have been the author. The very style suggests this conclusion; for it is distinctly scholastic, and proper therefore to a later age than that which aimed at the direct and simple reproduction of Eastern texts. It is satisfactory to find that this criticism, hardly convincing per se, is fully borne out by what occurs in the substance of the work itself. The author quotes from the De Mineralibus of Albertus. Now Albertus Magnus, by common testimony, produced this treatise after the year 1240, and we may anticipate what is afterwards to be told of Michael Scot’s death so far as to say here that he had then been long in his grave. The De Natura Solis et Lunæ then must be ascribed to some other and later alchemist, who lived in the end of the thirteenth or the beginning of the fourteenth century. A more careful examination of the treatise than has been necessary for our purpose might succeed in fixing its date with greater precision, and might possibly throw some light upon the person of its true author.

Another work ascribed to the pen of Michael Scot, and one which seems likely to be authentic, is that contained in the Speciale Manuscript. This volume is one of those collections of alchemical tracts made in the fourteenth century to which we have already alluded. It belonged to the library of the Speciale family in Palermo, and has been made the subject of an interesting monograph by Carini.[119] No. 44 of this manuscript is entitled Liber Magistri Miccaelis Scotti in quo continetur Magisterium. The term Magisterium, or supreme secret of art, would seem to carry with it a certain reference to Aristotle, ‘Il Maestro di color che sanno,’ as Dante calls him.[120] Curious as the appearance of such a name in connection with alchemy may seem to us, it is certain that Aristotle held a high place in the chemical traditions of the Middle Ages. The Meteora afforded a text which lent itself readily to large commentaries by the Arabian chemists. The tract De Mineralibus, which we noticed when speaking of Al Kindi, was one of these commentaries, and it is easy to see how it became confused with the text which it illustrated so as in time to be considered the work of Aristotle himself. This, we may believe, was the ground on which so many alchemical works were afterwards published under the same mighty name.[121] An interesting example appears in the Speciale collection itself which contains the following title: Liber perfecti Magisterii Aristotelis qui incipit cum studii solertis indigere.[122] The treatise Cum studii is also found in the Paris manuscript,[123] where it is ascribed to Rases. To the school of Rases then we are inclined to attribute the works on the Magisterium, and among the rest therefore, this treatise in the Speciale Manuscript, which bears the name of Michael Scot, seemingly because he translated it from the Arabic. This conclusion is confirmed when we notice the character of some of the chapter headings as given by Carini; for example: ‘Qualiter Venus mutatur in Solem’; and again, ‘Transformatio Mercurii in Lunam.’ These show beyond all doubt that the doctrine which Michael Scot published by means of this version was that held by the school of Rases.

A curious question here offers itself for our consideration. In the times of Robert Castrensis alchemy was as yet unknown to the Latins. Michael Scot, as we shall presently see, described it in one of his works as meeting with but a poor reception at its first introduction among them.[124] How then did it come to pass that in a few years the theory of Rases became so popular in the West, and continued for so many ages to direct the progress of chemical study among the European nations with enduring power? We find the explanation of this sudden change in the fact that human thought has always been subject to the tyranny of ruling ideas. In our own day the place of direction is filled by a doctrine of development which is eagerly made use of in every department of knowledge. In those earlier ages the same place seems to have been held by a doctrine of transformation. This idea ruled the thoughts of men like an obsession, in whatever direction they turned their minds. We see it in their superstitions, suggesting the wild tales of were-wolves and of other animal forms assumed at will by wizard and witch. We find it in religion, infusing a new meaning into the hyperbolical language of still earlier times, till, under this direction, there came to be fastened upon the Church a full-formed doctrine of Transubstantiation.[125] It is the operation of the same idea then that we are to remark also in the scientific sphere. As soon as the first shock of their surprise was over, the Latins greedily embraced a theory of chemical change which related itself so naturally to the prevailing habit of their minds, and which promised to show as operative in the mineral kingdom a law already conceived to hold good in the world of organic life.

The Riccardian Library of Florence possesses another of those volumes to which we have already referred: a collection of alchemical treatises formed in the end of the thirteenth or beginning of the fourteenth century.[126] Among these appears one called the Liber Luminis Luminum. It is said to have been translated by Michael Scot, and, as there is no reason to doubt this ascription, we have now the means of determining with some fulness and accuracy the lines on which the philosopher proceeded in his chemical researches.

The book opens with a preface somewhat scholastic,[127] and one which, on this ground as well as on others, is probably to be ascribed to Scot himself. In this part of the work he informs us that he took as his basis in the following compilation a text called the Secreta Naturae. To it he added material derived from other sources, which seemed necessary in order to complete the doctrine of chemistry contained in the Secreta. In this way he endeavoured to present his readers with a full and practical body of Alchemy according to the teaching of the school to which he belonged.

In the study of a composite work, such as the Liber Luminis is thus declared to be, our first problem is naturally to determine and separate the original text from the additions which have been made to it. Which then are those parts of the Liber Luminis that represent the Secreta Naturae? Very fortunately the volume where the Liber Luminis is found contains another treatise that throws considerable light on the matter. This is the Liber Dedali Philosophi. The correspondences between that book and the Liber Luminis are so many, close, and verbal, that it is evident both have borrowed from the same source. This source can hardly have been other than the Secreta Naturae, so that a comparison of these two books such as is attempted in the Appendix[128] should go far to determine what that hitherto unknown text was.

The question of the chemical doctrine contained in the Secreta is an interesting one, and we shall return to it, but meanwhile, let us observe that the Liber Luminis contains hints which seem to carry us further still, and throw some light upon the source from which the Secreta was itself derived. One of the authors quoted is a certain ‘Archelaus.’ Now there was a veritable chemist of this name who lived during the fifth century. This author wrote a treatise on his art in Greek verse. In later times his name seems to have become common property, as did so many others distinguished in alchemy, and to have been freely used by some who wrote long after his day. Thus the Riccardian manuscript itself contains no less than three books ascribed to this author: the Liber Archelai Philosophi de arte alchimiae,[129] called also in the margin Practica Galieni in Secretis secretorum;[130] the Summula, ‘quam ego Archilaus transtuli de libro secretorum’;[131] and finally the Mappa Archilei nobilis philosophi.[132]

The fact that these titles mention the Secreta is enough to show us that in following up the alchemy of the Pseudo-Archelaus, we are on the right track. As we proceed the traces become still more interesting and significant. The Summula offers the following curious passage: ‘Et hoc feci amore Dei et cuidam compatri meo, qui pauper sint [sic] et infortunatus, et postea fortunatus fortuna bona et amore Imperatoris Emanuelis et Frederici.’[133]

The name Emanuel is found in other alchemical writings. The De Perfecto Magisterio, for example, which has been reprinted by Zetzner, embodies another work, the Liber duodecim aquarum which is expressly said to be taken from the ‘Liber Emanuelis.’ Pursuing the matter further still, we come to the Liber Aristotelis which commences, ‘Cum de sublimiori atque precipuo.’ The author of this treatise, we find, claims not only the Liber duodecim aquarum (‘quae qualiter se habeant in libro quem XII. aquarum vocabulo descripsimus, prudens lector intelligere poterit’), but also, it would seem, the very one of which we are in search (‘in libro secretorum a nobis dictum est’). Everything inclines us to the belief that we here touch the source from which the main part of the Liber Luminis was drawn, and this conclusion is not a little strengthened when we observe that the treatise ‘Cum de sublimiori’ is called the Lumen Luminum in the Riccardian copy.[134]

The Secreta, however, was not the only source from which the Liber Luminis and the Liber Dedali were drawn, and the assertion of the preface that the former was composed of extracts from many different philosophers is fully borne out when we examine the substance of the books themselves. A strain of Greek influence is to be traced, for example, in the names of Archelaus, Dedalus, Plato, and Hermes, as well as in the use of ciatus as an equivalent for the word ‘cup,’ and this reminds us strongly of the Summula with its reference to the Emperor Manuel. It is not impossible that Scot may have borrowed much from the Byzantine chemists of the twelfth century. With this notion agrees the passage of the Liber Dedali where Saracens are spoken of as foreigners. On the other hand, much had evidently been taken from Arabic sources, as is plain from the names given to several of the vessels used in alchemy, such as the alembic and aludel. Indeed, Unay and Melchia, who are quoted in the Liber Luminis, must have been Moors, for the corresponding passage of the Liber Dedali describes them as from ‘Lamacha of the Saracens.’ Both these texts agree in showing such familiarity with the process of refining sulphur that one is led to suppose the Secreta, their common original, may have been composed in Sicily. The Liber Luminis says of one of the alums that it is ‘brought from Spain:’ an expression agreeing well with the notion of a Sicilian author, who would naturally speak of Spain as a foreign land.

Leaving, however, these questions of origin and derivation, let us come to that of the chemical doctrine taught in the book which Michael Scot compiled, or at least translated. The title of the Liber Luminis Luminum is a significant one, and has a real relation to the contents of the work itself.[135] To discover the sense which it must be held to bear we have only to turn to the passage in which, speaking of alum, the author says: ‘sicut illuminat pannos, ita illuminat martem ut recipiat formam lunae. Ut enim lana illuminatur ita et metalla illuminantur.’[136] A distinction is clearly present in the writer’s mind between the substance and the form of the metals. He probably held that there existed but one common metallic substance, which assumed the appearance of iron, gold, or silver, according to the form which it had received. His employment of the title Liber Luminis Luminum was meant to indicate that the purpose of his book was that of teaching the student how metals might best be purified and improved. Their inferiority, when of the baser kind, he conceived as an impurity, manifesting itself in the imperfect forms of lead, iron, tin, and copper. He believed that this being removed or changed by art, they might be made to shine with the lustre and indeed possess the only distinctive quality of gold and silver. That we have rightly read the meaning of this title seems plain from a curious spelling which may be noticed in the Liber Dedali. ‘Illuminantur’ there appears as ‘aluminantur.’ The chemistry taught in these books did in fact prescribe the use of alum as a great means of purifying and refining the metals.

The preface of the Liber Luminis closes with a brief summary of the chapters which compose the work itself. The first of these deals with the different salts used in this chemistry: common salt; rock salt; alkali; sal ammoniac; nitre and others. The second treats in like manner of the various kinds of alum, the third describes the vitriols, and the fourth the powders or spirits, by which we are to understand those minerals which are capable of being sublimed or made volatile, such as sulphur, arsenic, and mercury. Two supplementary chapters, the one on the preparation of the salts, alums, and vitriols, and the other on that of the remaining class of chemicals, complete the whole book. This supplement seems genuinely such, as it is not mentioned in the general contents, as these appear in the preface. Perhaps we do not err if we suppose it to have embodied the result of Scot’s own experiments in alchemy.

It is indeed the practical nature of the alchemical doctrine taught in the Liber Luminis which strikes us most strongly when we read this book. A large part of it is taken up with exact descriptions of the minerals, according to their various forms and the countries from which they were derived. The rest consists of receipts for their employment in refining metals. Whatever we may think of the validity and use of these processes, we cannot fail to notice that they are described in a perfectly straightforward and simple style. Here are none of the mysteries, the riddles and ridiculous allegories so common in chemical works written at a later time. The truth of the matter may probably be that, in following the doctrine here set forth, Michael Scot and the alchemists of his time did obtain results which were then so surprising, as to excuse a certain exaggeration in those who described them. Tests that could touch and reveal the real nature of the metals under any change of outward appearance were not then so well known as now. Copper that had been made to shine like gold, or to assume the appearance of silver, was practically gold or silver to those who had no means of discovering that the real nature of the metal itself remained unchanged. Thus then are to be understood the assertions of the Liber Luminis regarding transmutation. They are plainly made in all good faith, and depend on the doctrine already mentioned, which held that the differences between the metals were an affair of the superficial form rather than of the underlying substance. To change the appearance of one metal to that of another, was therefore to effect a real transmutation: the only one conceivable by the philosophers of that time. When the Liber Luminis speaks of giving copper ‘a good colour,’ or preparing iron to ‘receive the appearance (formam) of silver,’ these expressions reveal with frank sincerity the conceptions of this alchemy and the results it endeavoured to obtain.

One other alchemical work attributed to the pen of Michael Scot remains to be noticed; the De Alchimia, contained in a manuscript of Corpus Christi College, Oxford.[137] Tanner in his Bibliotheca has noticed this work in the following terms: ‘Chymica quaedam ex interpretatione Michaelis Scoti dedicata Theophilo regi Scotorum. Corpus Christi MS. 125. In eodem codice MS. fol. est haec nota “Explicit tractatus magistri Michaelis Scoti de aelchali,” huius vero tractatus, a priore diversi, hoc tantum fol. extat.’ This account is erroneous in several particulars. ‘Scotorum’ should be ‘Saracenorum,’ and ‘de aelchali’ is a misreading of ‘de alkimia,’ as a glance at the manuscript informs us. Nor is it the case that we have here to deal with two distinct works. The last leaf, to which Tanner more particularly refers (fol. 119, old numeration), shows a hand of the fourteenth century, and forms the only remainder of the original. The rest of the manuscript (fol. 116-118) has been supplied by a scribe of the fifteenth century, but the whole is perfectly continuous, as appears plainly when we notice that the first words of the original (fol. 119 recto), ‘et cum siccatus,’ have also been written by the later scribe at the bottom of page 118 verso.

In spite of the highly suspicious dedication, ‘Theophilo Regi Saracenorum,’ several reasons incline us to regard the De Alchimia as, in substance at least, a genuine work of Michael Scot. To begin with, it clearly belongs to a very early period; for, in the opening words of his preface, the author describes alchemy as a science, noble indeed, but as yet neglected and contemned by the Latins (‘apud Latinos penitus denegatam’). In the same sentence we find him referring to the secreta naturae, just as Scot does in the Liber Luminis, and declaring his purpose to furnish the world with a commentary on it in the work he now attempts (‘secreta naturae intelligentibus revelare’). In the opening paragraph of the book itself he seems to refer plainly to the Liber Luminis as a work written by him (‘notitia de salibus vel salium prout in aliquo libro a me translato dixi’). Nor should we overlook the distinctly ecclesiastical tone which is to be observed in the De Alchimia. Part of the preface is conceived almost in the form of a prayer, commencing thus: ‘Creator omnium rerum Deus qui cuncta ex nihilo condidit,’ and in at least one passage, a well-known text of Scripture is reproduced (‘et haec est res quae erigit de stercore pauperem et ipsum regibus equiparat’). This style is a noticeable characteristic of all the works of Michael Scot.

On the other hand, the De Alchimia shows several doubtful features which, on the supposition that it came from Scot’s pen, can only have been due to some interference with the text at a subsequent time. Such is the dedication to Theophilus, King of the Saracens, which we have already noticed, and the latter part of the preface shows a turgid passage (‘hic est puteus Salomonis et fimi acervus, et hic est fons in quo latet anguis cuius venenum omnia corpora interficit,’ etc.) that strongly recalls the fancies of the later alchemy.

The body of the work, however, is no doubt genuine, and offers matters of considerable interest. The first of these is perhaps the distinction drawn here between the greater and the lesser mystery (magisterium) of alchemy. The former, it seems, was the transmutation of Venus into the Sun; that is, of copper into gold. The latter comprehended the fixation of mercury and its transmutation into the Moon, or silver.

We soon notice too that the author addresses himself not, as one would at first expect, to ‘Theophilus,’ but to a certain Brother Elias (‘tibi Fratri Helya’)—another proof, if any were needed, that the dedication to the apocryphal King of the Saracens was due to some other and later hand. ‘Brother Elias,’ however, was far from being a merely imaginary personage. He was an Italian, born (for accounts vary) either at Bivillo near Assisi, Cellullae or Ursaria near Cortona, or in Piedmont. In 1211 he joined the Order of St. Francis, then just formed, thus becoming one of its earliest members. His history as a Franciscan was rather an eventful one. On the death of St. Francis in 1226 he succeeded the Founder as General of the Order, but was deposed by the Pope in 1230 on some suspicion that he favoured schism among his brethren. The Order re-elected him in 1236, but he was finally removed from office by Gregory three years later, and profited by the occasion to join himself openly to the party of the Emperor. For this he suffered excommunication in 1244, and was not restored to the privileges of the Church till 1253, when he lay on his death-bed at Cortona. There is no doubt that he had the reputation of possessing skill in alchemy, as a treatise is extant called the Liber Fratris Eliae de Alchimia.[138] This renown would not tend to his honour in religion. It seems indeed to invest with a cruel and pointed meaning the words used by the Pope on the occasion of his first deposition.[139] He is said to have been sent in early days on an embassy to the Emperor of the East. Perhaps this may have been the occasion when he first acquired a taste for those chemical studies which that nation still pursued. Michael Scot addresses him in the De Alchimia as a pupil (‘Et ego, Magister Michael Scotus, sum operatus super solem, et docui te, Fr. Elia, operari et tu mihi saepius retulisti te instabiliter multis viabus operasse’), while at the same confessing that he was not above learning some of the secrets of art from the well-known Franciscan. This relation between two such distinguished men has not hitherto been noticed, and is certainly a curious point in the history of the times.

The De Alchimia presents several features which distinguish it from the Liber Luminis. One of these is an early passage which refers to the correspondence between the metals and the planets, and explains that when the latter are named we must understand that the former are intended. Near the end of the treatise a description of the materia chemica occurs, but it would seem as if this had been written to supplement that given in the Liber Luminis, for it deals, not with salts, alums, vitriols, or volatile substances, but with the different varieties of what the author calls ‘gummae,’ which, however, are mineral substances;[140] and with ‘tuchia’ in all its various kinds.

Many words and phrases, however, might be cited to show how the strain of doctrine observable in the Liber Luminis is continued with scarcely any change in the De Alchimia. We have hardly read a line in the first receipt before we meet with the expression ‘sanguinem hominis rufi’ recalling the ‘sanguinem hominis rubei’ of the Liber Luminis. The ‘pulvis bufonis’ indeed is here replaced by another ingredient derived from the animal kingdom, the ‘sanguis bubonis’; but, reading a little further, we find the familiar ‘urina taxi’ again recommended as an almost universal solvent and detergent. Evidently both works proceeded from one and the same alchemical school. The number of Arabian chemists[141] cited in the De Alchimia seems to show that if these books came from a Greek source it was not that of ancient times, but some Byzantine school that had borrowed much from Eastern alchemists.

To give a substantial idea of the De Alchimia let us translate one of the formulae which it contains: ‘Medibibaz the Saracen of Africa used to change lead into gold [in the following manner]. Take lead and melt it thrice with caustic (‘comburenti’), red arsenic, sublimate of vitriol, sugar of alum, and with that red tuchia of India which is found on the shore of the Red Sea, and let the whole be again and again quenched in the juice of the Portulaca marina, the wild cucumber, a solution of sal ammoniac, and the urine of a young badger. Let all these ingredients then, when well mixed, be set on the fire, with the addition of some common salt, and well boiled until they be reduced to one-third of their original bulk, when you must proceed to distil them with care. Then take the marchasite of gold, prepared talc, roots of coral, some carcha-root, which is an herb very like the Portulaca marina; alum of cumae something red and saltish, Roman alum and vitriol, and let the latter be made red; sugar of alum, Cyprus earth, some of the red Barbary earth, for that gives a good colour; Cumaean earth of the red sort, African tuchia, which is a stone of variegated colours and being melted with copper changeth it into gold; Cumaean salt which is …; pure red arsenic, the blood of a ruddy man, red tartar, gumma of Barbary, which is red and worketh wonders in this art; salt of Sardinia which is like …. Let all these be beaten together in a brazen mortar, then sifted finely and made into a paste with the above water. Dry this paste, and again rub it fine on the marble slab. Then take the lead you have prepared as directed above, and melt it together with the powder, adding some red alum and some more of the various salts. This alum is found about Aleppo (‘Alapia’), and in Armenia, and will give your metal a good colour. When you have so done you shall see the lead changed into the finest gold, as good as what comes from Arabia. This have I, Michael Scot, often put to the proof and ever found it to be true.’

If such a receipt is valuable as indicating the chemical practice of those days, it is no less interesting as it throws light upon the life and occupations of Scot. He must have set up a complete chemical laboratory at Toledo, with crucibles for the melting of metals, and alembics for the distillation of the substances which his art required him to mix with them. His situation was one very favourable to these pursuits, not only because Spain was one of those countries where the doctrine of alchemy made its greatest progress, and attracted most powerfully the concourse of foreign adepts, but also from the facility with which the necessary materia chemica could there be procured. The sierras of that country were full of mineral wealth of all kinds, especially quicksilver, which was one of the substances most frequently chosen to become the subject of the transmuter’s art. In the Alpujarras, a mountainous district lying under the soft climate of Granada, grew plenty of these rare herbs employed in alchemy, as they were also in the medicine of the Arabians. Ibn Beithar of Malaga describes them in his botanical thesaurus, and it is said that after the Moors had lost that fair kingdom their herbalists, even as late as our own times, made yearly journeys from Africa to gather in these hills the plants which ancient science taught them to value highly. But the days of the ‘ultimo sospiro del Moro’ were yet in the far future, and meanwhile Michael Scot in his laboratory at Toledo could easily command all these treasures for the purposes of experiment. Nor was it in vain that he fanned his fires, and watched the metals melt and the menstruum distil in the process of the lesser or greater mystery. If he never saw Venus blush into the true substance of Sol, or Mercury, the fickle and obstinate, congeal into a veritable Luna, his chemical practice, and the records in which he has embodied it, mark none the less true and significant a moment in the history of scientific progress.

CHAPTER V
THE ASTRONOMICAL WRITINGS OF SCOT

The alchemy of the thirteenth century, to the progress of which Michael Scot contributed not a little, bore a close relation to the opinions then entertained in another branch of science: that of astronomy. We have already noticed how chemistry, as practised in Egypt, was largely influenced by Eastern theories regarding the stars and their power over earthly elements. That this connection and sympathy was still a matter of common belief at the time Scot wrote is not only probable but can readily be established by direct evidence. The treatise ‘Cum studii solertis indagine,’ already referred to,[142] has a curious passage which bears directly on the point in question. We find in the preface the following remarkable statement: ‘For the art of alchemy belongs to the deeper and more hidden physics, and in particular to that division thereof which … is called the lower astronomy,’ It is plain then that no chemist could in those days be considered fully competent for the task he undertook unless to a knowledge of the customary theories and processes of his art he added some acquaintance with the mysteries of the heavenly spheres as well.

To Michael Scot, even before he came to Toledo, the science of astronomy was already a beaten path. His progress in mathematical studies naturally led him to this, the highest sphere in which they could be exercised. At the court of Frederick he had made many an observation and cast many a horoscope. In the Liber Introductorius and Liber Particularis he had produced two manuals expounding in a popular way the twin sciences of astrology and astronomy; publications which no doubt reproduced pretty exactly the teaching he had given to the Emperor.

In Spain he not only kept up his interest in this subject but lost no opportunity of improving his past acquirements. He was constantly on the watch for new astronomical works. He read them, not only as a student eager to extend his knowledge, but as a translator anxious to find the opportunity of adding to the resources of other scholars by the production of some important book in a Latin dress.

As a resident in Toledo, Scot found himself very favourably situated for such studies. That city was now indeed to become what may be called the classic ground of Moorish astronomy. A Spanish author would have us believe that there presently assembled there an incredible number of astronomers drawn, not only from all parts of Spain, but from France as well, and especially from Paris. The king himself is said to have presided over this congress. The works of Ptolemy, with the commentaries of Montafan and Algazel, were translated into Latin for the use of those scholars who did not understand Arabic. Discussions were held in the Alcazar of Galiana upon the various theories of the heavenly bodies and their movements. These labours, which commenced in 1218, and are said to have lasted till 1262, resulted in a more exact series of observations than had hitherto been made. They were published, and became generally known as the Tables of Toledo.[143]

It was in such a direction indeed that the line of true progress lay. As alchemy rose into a real chemistry rather by the practice of the laboratory than by the theory of the schools, so it was with regard to astronomy. The scheme of Ptolemy with its various modifications necessarily held the field, imperfect and erroneous as it was, till wider and more exact observations, such as those for which the wise king of Castile thus provided had, in the course of after ages, furnished adequate ground for the magical and illuminative speculations of Copernicus, Galileo, and Newton.

Favourable, however, as Scot’s situation in Toledo undoubtedly was, much of what we are considering lay beyond his reach, being yet in the womb of the future. The Moorish astronomers, and he doubtless with them, felt far from satisfied with the Ptolemaic system as expounded in the Almagest. While no one as yet ventured to interfere with its fundamental conception of the earth as the centre of the universe, every fresh observation, by bringing into view more of the delicacy and subtlety of the heavenly movements, made additions and modifications of that theory constantly necessary. Hence arose a series of Arabian works on the sphere, each superseding that which had preceded it, and reflecting the last results obtained with the astrolabe. Such a line of progress could not but lead to the time when the Ptolemaic theory no longer lent itself by any modification to the full explanation of ascertained facts. Then and then only arose the new astronomy of the sixteenth and seventeenth centuries, which is thus seen to be vitally connected, even in its highest reach and most splendid developments with the now forgotten theories of the Moorish schools.

Considering then the epoch at which he lived, and the incomplete material which existed in his days for a true science of the heavens, Michael Scot did all that could be reasonably expected of him. He sat at the feet of those who were then the best authorities on this subject. He used his opportunities at Toledo to make the last and most subtle theories of the Moors intelligible to those less fortunate scholars whose attention these must otherwise have escaped.

His services to astronomy appeared in the Latin version which he made from a treatise on the Sphere lately composed by Alpetrongi. This author’s name is said to have been, in its Arabic form, Nured-din el Patrugi. Munk, in his Mélanges, tells us that the latter designation was derived from a village called Petroches lying a little to the north of Cordova.[144] The Latins corrupted the name in different ways, so that among them it became Avenalpetrandi, Alpetrongi, or Alpetragius. The astronomer who bore it flourished about the year 1190, and is said to have been a renegade, and a scholar of the celebrated Ibn Tofail, the author of the curious Sufic romance called Hay Ibn Yokhdan.

In the preface to his book on the Sphere Alpetrongi begs to be excused if he has ventured to differ from the tradition of the ancients in his theory of the heavenly movements, and especially from Ptolemy the great master of this science. His apology reminds us that it may be well to examine more exactly than we have yet done the various advances which had been made up to this time by the Arabian astronomy.

As early as the ninth century the mathematicians of that nation had simplified the problems of the circle by discovering the way of measurement by sine and tangent instead of by the chord. This improvement is ascribed to Albategni who lived between the years 877 and 929. Calculation was soon made still easier by the invention of algebra. The year 820 is given as the age of Mohammed ben Moussa, surnamed Al Khowaresmi, who had the honour of this important discovery. From the surname of this mathematician the Latins afterwards formed by corruption their common noun Algorisma or Algorithmus, from which our word arithmetic is derived.

These improved methods of calculation were soon applied to astronomy. Al Mamun, whose reign commenced in the year 813, summoned an assembly of scholars learned in that science. They met in the great Babylonian plain, having chosen that place as suitable for their observations, and measured the declination of the ecliptic, which they determined to be 23° 33ʺ. About the same time the secular motion of the heavens began to attract attention. Albategni corrected the observations of Ptolemy here, and showed that the retrograde movement amounted to one degree, not in a century as the Greek philosopher had said, but in a shorter period which is variously stated as sixty-six or seventy years. Alfargan repeated this calculation, and amended that relating to the declination of the ecliptic, which he computed at 23° 35ʺ.

This was the progress and these the data which led the Moorish astronomers to abandon the earlier and simpler theories of the sphere as inconsistent with ascertained facts. They were aware of motions among the heavenly bodies not to be explained by the mere supposition that round the earth as a centre moved the concentric spheres on the axes of their poles. It is true that even Ptolemy himself had felt something of this difficulty and had endeavoured to meet it by a theory of eccentrics and epicycles. As knowledge increased, however, this primitive explanation was felt to be cumbrous and unsatisfactory. Aboasar[145] and Azarchel gained fame by boldly striking out in new paths, and later Moorish astronomers eagerly followed the lead thus given them, each adding some modification of his own.

Thus then we return to the preface of Alpetrongi prepared to understand his position when he declares himself obliged to depart from previous traditions. He proceeds to avow himself a scholar of Azarchel, but when we examine his work we find that the theory he proposes differs considerably even from that taught by his immediate master. It was one which, through the labours of Michael Scot, as translator of Alpetrongi, exercised no small influence on the study of astronomy among the Latins, and we may well spend a moment in considering the chief features which it presents.