The discoveries of Al-Hazen in optics, communicated to Europe by the Spanish and Sicilian Mohammedans, have had a marked effect on the development of that science, and are the basis of all that we know on the subject. He understood the cause of the twilight; estimated the density and calculated the height of the atmosphere. He explained by the principle of refraction why celestial bodies are visible when they are actually below the horizon. He discussed the effect upon vision of the varying transparency of the air, and suggested that beyond our atmosphere there was nothing but ether, a proposition which modern astronomy accepts. First of all investigators, he corrected the prevalent fallacy that the rays of light proceed from the eye to the object seen, an error which had hitherto deceived all who had written on the science of optics. The works of Al-Hazen were used as text-books in the Andalusian colleges, and they were first made known to Christendom through the foreigners who came to study Arabic learning in the schools of Toledo. Among such literary pilgrims of the twelfth century were the Englishmen Adelard of Bath, Robert of Reading, Daniel Morley, William Shelley, and the Italian Gerard of Cremona. The translations of Arabic works into Latin introduced by the labors of these and subsequent scholars in the department of medicine alone amount to nearly four hundred.
Great as was the reputation of these ambitious ecclesiastics among the ignorant masses of their countrymen, it did not approach that of the famous Gerbert, whose genius had unsuccessfully attempted the enlightenment of Europe nearly two hundred years before. The attainments of that accomplished scholar, respectable in any age, were so superior to those of his contemporaries that, as has been previously stated, they procured for him the unenviable and dangerous title of magician. A native of Aquitaine, of obscure birth and without resources, his talents early attracted the notice of the Count of Barcelona, who provided for his education in that city. Thence, after a time, he visited the principal Moorish cities of Andalusia. It was the tenth century, the epoch of the highest prosperity and magnificence of the Ommeyade Khalifate. Everywhere were visible the effects of that civilization which had no rival in the world. The thorough agricultural development of the country; the busy seaports; the luxurious palaces; the populous cities; the well-paved streets, filled by day with surging multitudes, and lighted at night by tens of thousands of twinkling lamps; the illimitable expanse of verdure which marked the environs of the great Moorish capital, broken only by occasional watch-towers and gilded minarets; the gorgeous splendor of the court; the prodigious libraries; the innumerable schools and colleges, equipped with every scientific appliance known to Moslem culture—colored maps, armils, sundials, clepsydras, hydrometers, parallactic rules, quadrants, astrolabes, planispheres, globes; the mosque with its throngs of pilgrims gay with the costumes of every land acknowledging the creed of Islam,—these scenes did not fail to profoundly impress the young French ecclesiastic, already imbued with prohibited ideas and fresh from the intolerance, the barbarism, the credulity, and the intellectual debasement of Christian Europe. The mind of Gerbert was prompt to recognize the manifold advantages to be derived from familiarity with Moslem institutions and erudition. He became a student of the University of Cordova. During the few years he remained in that city, his talents and perseverance procured for him a fund of scientific information unexampled for that period. On his return he established schools in both Italy and France. He imported books from every quarter of the world, and especially from Spain. His pupils, reckoned by thousands, diffused throughout Europe the fame of their teacher and the precepts of his works. The instruction he imparted embodied the forbidden learning taught beyond the Pyrenees. He was the first to explain to Europeans the abacus, the Indian numerals, the science of arithmetic. He taught geography and astronomy from globes constructed at Cordova. He observed the motions of the planets and determined the elevation of the pole through diopters. The results of the mechanical ingenuity which amused his leisure moments awakened the horror of his ignorant and pious contemporaries. He invented a steam or hydraulic organ; a clock whose mechanism was largely composed of wheels and pinions; and automatons whose mysterious movements suggested to the vulgar a diabolical agency. He improved the science of music. His system of imparting knowledge, based upon experiment and demonstration, exhibited a radical difference from the prevalent methods of an epoch whose instruction was limited to Scriptural texts and ecclesiastical admonition. The renown of the great scholar excited the envy of the monks, to whom the popular imputation of infernal communion afforded a pretext for persecution. They instigated marauders to plunder his abbey at Bobbio, in Italy. His library was burned, his instruments were destroyed, his students dispersed. This ill-treatment, so far from being, as intended, prejudicial to the fortunes of Gerbert, ultimately promoted them. His reputation was everywhere known, and the awe his wisdom excited was increased by the supernatural means he was believed to employ. He was patronized by the King of France and the Emperor of Germany; he became successively Bishop of Rheims and of Ravenna; and, through the influence of the latter sovereign, he was, in the year 999, raised to the pontifical dignity, under the name of Sylvester II. Even in that exalted position, the relentless spirit of ecclesiastical malice did not permit him to rest. His attempts to reform clerical abuses brought down upon him the vengeance of the corrupt and rapacious ministers of the papal court. The most absurd fables were invented to account for the results of his scientific experiments, otherwise incomprehensible by mediæval ignorance. He was accused of gross immorality, blasphemy, magical incantations, the invocation of demons. It was whispered that goblins of fantastic dress and repulsive aspect attended him at midnight during the celebration of impious orgies and profane sacrifices. The diligent propagation of these scandals prepared the way for the punishment meted out in that age to all daring reformers, and especially to those who presumed to interfere with the prerogatives and emoluments of the clergy. A victim of slow poison, Sylvester II. survived his elevation to the Papacy less than four years. His name was anathematized, his doctrines condemned as heretical, and the perusal of his writings prohibited as contrary to the canons of the Church and prejudicial to the interests of religion. After his decease, a long period of darkness again clouded the Christian world. The dawning spirit of inquiry thus suppressed, men once more turned to the priest for counsel, for assistance, for the explanation of natural phenomena, for the cure of disease. Such was the inauspicious and apparently futile result of the first introduction of Arabian learning into Roman Catholic Europe.
The unrivalled excellence of the agricultural methods employed by the Spanish Mohammedans was, in large measure, due to their profound botanical knowledge. That science, practically unknown in the desert wastes of Arabia, to which nature has begrudged the wealth of her vegetable kingdom, was early pursued with great energy and success by the conquering Moslems. In no other part of their empire, however, was such progress made in its study or such beneficial results obtained from the culture of plants as in Andalusia. Their analysis and classification, and the determination of their properties, were sedulously encouraged by the government. The scientific expeditions of the khalifs collected specimens and seeds from every quarter of the world. Gardens for the propagation of both native plants and exotics were established in the environs of all the great cities, and the results of intelligent observation and experiment were regularly tabulated for the public benefit. In the oases of the Desert, along the banks of the Nile, on the fertile plains of Mesopototamia, on the arid plateaus of Central Asia, in the pestilent delta of the Ganges, the botanists of Cordova added to the stock of ideas and principles to be subsequently developed and advantageously applied in the valley of the far distant Guadalquivir. Nor were their efforts confined to the mere collection and examination of products of the vegetable kingdom. Every novel appliance, every useful invention, which might prove beneficial to horticulture, to irrigation, to the various branches of rural economy, were diligently noted and carefully preserved. As a consequence of these laborious researches, the Andalusian Arabs became more proficient in the kindred sciences of botany and agriculture than any people who have ever existed. In their country were concentrated all the fruits of the learning and experience of centuries then extant in the world. It is said that they added to the herbals of the ancients more than two thousand varieties of plants. They described the circulation of the sap; they understood the offices of the bark and the leaves. Every source of information was thoroughly explored. Already, in the tenth century, the treatise of Dioscorides had been translated into Arabic by a monk of Constantinople, sent by the Emperor at the special request of the Khalif, because the subjects of the latter were ignorant of Greek. The botanical works of the Hispano-Arabs were enriched with drawings from nature, beautifully executed in colors. When Ibn-Beithar, of Malaga, the most famous of Moslem botanists, travelled in the Orient, he was accompanied by a corps of artists, whose skill preserved the form and tints of unfamiliar flora in all their beauty and perfection. His is the greatest name in the annals of this important branch of learning from Dioscorides to Linnæus, an interval of fifteen hundred years.
In the wide range of philosophical and experimental study, however, no subject was so congenial to the taste of the Arab or appealed more strongly to his imagination than the pursuit of the spurious science of alchemy. That science originated in Egypt, the land of isolation, of enchantment, of prodigy. Its investigation, confined to a privileged class, had been protected by the double safeguard of religion and secrecy. For innumerable centuries the Egyptian priesthood, the sole depositaries of knowledge, had, in laboratories hidden in temples or excavated in the rocky sides of mountains, eagerly devoted themselves to the discovery of the universal panacea, of the elixir of life, of the transmutation of inferior metals into gold. The Ptolemaic dynasty, heir to these delusions so acceptable to human egotism and avarice, had contributed to their universal dissemination over Europe and Asia. The Arabs, from the first hour of their intellectual emancipation, prosecuted with alacrity a study especially adapted to their national inclination and genius. The fact that the Koran prohibits such occupations made their association with religion, contrary to the custom in Egypt, impracticable. At Toledo and Cordova, alchemy was not designated, as at Memphis and Thebes, the “Sacred Art,” cultivated in the precincts of temples, communicated only to royalty, screened from the profanation of the vulgar by the delusive mummeries of processions and sacrifices. Its close relations with thaumaturgy and divination, with astrology and magic, were inevitable consequences of the uncertainty of its results, and of the mystery that enveloped its professors. Ancient Hebrew tradition, as disclosed by the apocryphal books of the Bible, asserts that the occult arts and sciences were the gift of evil spirits to the children of men. The Romans punished such practices with death, probably for the reason that they came into competition with the oracles, a fruitful source of revenue and prestige to the state. Thus, in a measure, placed under the ban of religion and law, a subject of suspicion and fear to the masses, the study of alchemy was fraught with danger, even amidst the Pagan associations of antiquity. In the Middle Ages, the endangered interests of priestcraft added to legal prohibition and the prejudice of public opinion the resistless force of their condemnation.
The Spanish Arabs, passionately fond of experiment and novelty, were eminently proficient in the technicalities of the Hermetic Art. They entertained the idea that the same elements, in different proportions, were present in all metals, and that, by certain processes of elimination, any metal,—as, for instance, gold,—could be obtained. Like their masters, the Alexandrian Greeks, they concealed their discoveries in the obscurities of a learned jargon. The principles of their calling were indicated by mysterious symbols, enigmatical phrases, mutilated formulas, capable of interpretation only by themselves. With the advancement of learning, the operations of the alchemist were practised with less concealment and mystery. His labors were encouraged by the khalifs, of whom some were themselves adepts, and prosecuted their investigations in well-equipped laboratories. The prevalence of one delusion led to the propagation of others, and the original objects of alchemical research became confounded with astrology, mysticism, and all their chimerical relations and incidents,—theories involving the seven planets and the seven metals, the ceremonies of exorcism, the procuring of happiness by the identification of the soul with the Universal Intellect. Attracted by the profits to be obtained from human credulity, a swarm of charlatans sprang up in every community,—prototypes of the impostors who infested the society of Europe during the fourteenth and fifteenth centuries. Among these the Jews attained an unenviable notoriety, a reputation destined in subsequent ages to produce most deplorable consequences. Even under the Pharaohs, Hebrew astuteness had succeeded in penetrating the well-guarded arcana of the Egyptian priesthood. It was mainly through their traditional avarice that the precepts and formulas of the Sacred Art, divulged to the Greeks and afterwards to the Arabs, became the property of mediæval Europe. In Mohammedan Spain the Jews excelled in this unpopular but lucrative profession, as they did in every pursuit requiring intelligence, energy, craft, and skill. From this confused medley of philosophy, magic, and imposture were unconsciously obtained results of superlative value to the human race. The adept, poring over his retorts and crucibles in vaulted chambers far removed from inquisitive eyes, stumbled upon discoveries more important than that of the philosopher’s stone. In attempts to accomplish the transmutation of metals, processes were invented by which the analysis, separation, and smelting of ores were, hundreds of years afterwards, facilitated, and the visionary aim of the alchemist, in a measure, accomplished. From these secret experiments came the knowledge of the working of metals, of the composition of alloys, of the fusing of glass, of the application of enamels. Alchemy was thus the precursor of chemistry, and, so intimately are their principles and relations connected, that it is impossible to determine where the false science terminates and where the true science begins. The Hispano-Arabs carried the operations of both to a point not hitherto attained by the experimenters of the ancient world. While they profited largely by the learning of the East, it would be unjust to deny them the merit of conspicuous and striking originality. They practically invented modern chemistry. Their writers describe with clearness and precision the processes of crystallization, sublimation, distillation, filtration, solution. They introduced nitric and sulphuric acids, those powerful solvents, without whose agency chemical combinations could not be effected. To them is due the discovery of alcohol, muriate of ammonia, potassa, bichloride of mercury, nitrate of silver, and phosphorus. The adaptation of these substances to the multifarious purposes of daily existence has bestowed upon the inventor almost boundless resources for the development of the industrial arts, and has provided the surgeon with efficacious means of alleviating human suffering. The use of caustics and acids produced a revolution in medicine, and the skill of the physician, even in Christendom, was no longer classed with the exorcisms of the necromancer or subordinated to the mummeries of the priest. The Moslems of the Peninsula were aware that a calcined metal gains instead of loses weight, a fact whose knowledge foreshadows an acquaintance with gases and the discovery of oxygen; nor were they ignorant of the existence and the properties of hydrogen. Processes for the oxidation of metals and for the generation of gases are first mentioned by Djabar-al-Kufi, or Geber, whose personal history is unknown, and who is often confounded with the mathematician, Djabar-Ibn-Aflah, of Spain. The greatest Arabian chemist of any age, his abilities have been recognized and his name has been mentioned with respect by every investigator of the exact and experimental sciences down to the present day. It has been well said that he bears the same relation to chemistry that Hippocrates does to medicine. His writings—calm, judicious, eminently logical—are not obscured or disfigured by the absurdity and charlatanism of the epoch. Aside from his reference to the generation of gases by heat, and the radical alterations undergone by the substances from which they are derived, his fame would have been permanently established by his discovery of nitric acid and aqua regia, products of the laboratory not previously described by any author. Thus the philosophical methods of the Spanish Moslems gradually developed the visionary operations of alchemy into the science of chemistry. To the latter, however, still clung numerous indications of an origin fraught with imposture. Important experiments were deferred until the planetary influences were declared to be auspicious. The elixir of life was sought for with undiminished ardor. Monarchs were still deluded and plundered by means of fallacious promises of wealth to be obtained by the transmutation of metals. But, in many respects, notable changes were discernible, harbingers of incalculable benefit to both the physical and intellectual condition of humanity. Then was first effected the permanent separation between experimental science and religious mysticism, a union fatal to mental development and to the arts of civilization. From the earliest times, every important undertaking had been invested with a sacred character, and supplemented with ceremonies adopted to avoid publicity and to enhance its mysterious significance. It was no longer accounted sacrilege to explain the secrets of nature or necessary to enshroud the discoveries of the philosopher with the terms of an allegorical jargon. The scientific lectures of the Moorish universities of Spain were open to all students; the analyses of the laboratory were daily performed in the presence of thousands. Familiarity with its operations, experience of its advantageous application, diminished in time the suspicion with which chemistry was viewed by the populace. That science, necessarily slow in its development, originally based upon erroneous principles, profiting by the opportunities of accidental discovery, retarded by innumerable failures, hated by the priesthood, feared by the ignorant, classed as diabolical by the superstitious, was far from possessing the capability for progressive advancement and permanence of which mathematics was susceptible. Although practically its inventors, the Arabs paid more attention to the adaptation of its discovery to medicine than to the improvement of its processes or the purification of its products. This predilection induced them to separate pharmacy from chemistry as well as from medicine, thus creating a new and most important branch of science, of universal application and of practical benefit.
Europe is indebted to the Moslems of Spain and Sicily for the introduction of such drugs as nux vomica, cassia, croton, tamarind, myrrh, sandal, cubebs, ergot, senna, rhubarb, and camphor; for such spices as cloves, nutmeg, ginger, and cinnamon; for such compounds as juleps, elixirs, syrups, and electuaries, still known to commerce by their Arabic names. Under the khalifs, pharmacies were established in all the principal towns of the empire, subordinated to great central depôts at Toledo and Cordova. These were placed under government supervision, were visited by inspectors, and their owners held accountable for the purity of their commodities and the methods of their preparation. In Sicily the laws were even more stringent: every dispenser of drugs was subjected to a rigid examination as to his qualifications, and the professional oath of the physician required him to denounce to the proper authorities any pharmacist whose wares were inferior in quality to the regular standard. In addition to these salutary precautions against dishonesty and fraud, a scale of prices, publicly displayed, prevented extortion; and violation of the law subjected the offender to serious penalties. These regulations, adopted in the thirteenth century by the Emperor Frederick II., contributed greatly to the success attained by the medical schools of Salerno and Naples, and made Sicily the most famous market for medicaments in the world.
It is a remarkable circumstance that the science of the Saracens was largely diffused among the nations of Northern Europe through the agency of the ecclesiastical order, to whose faith, organization, and traditions it had always evinced an implacable hostility. The general dearth of educational facilities in the Middle Ages, the monopoly by the clergy of such learning as existed, and the fact that, among the latter, would be found, sooner or later, superior minds dissatisfied with the ignorance and the absurdities of the Fathers, were conditions that inevitably tended to this result despite the anathemas of pontiffs and the decrees of synods. Many of these innovators came from the monastic orders. It must not be forgotten that both Savonarola and Bruno were Dominicans. For more than a century there emanated from Toledo translations into Latin of classical works that had long before been rendered from Greek into Arabic. The pioneer of this intellectual movement was Archbishop Raymond, a Frenchman. His example was followed by Herman of Dalmatia, Michael Scott, and John of Seville. The three greatest Christian disseminators of the science derived from the Moors, however, were Albertus Magnus, Bishop of Ratisbon; Robert Grossetête, Bishop of Lincoln; and Roger Bacon, professor in the University of Oxford, all of the thirteenth century. The first is popularly known to posterity as an alchemist and a magician. He was, besides, a man of extensive knowledge, and a writer of voluminous treatises on theology, philosophy, alchemy, and chemistry. He described successfully the action of acids, the character of alkalies, the forms and alloys of metals. The method used to-day in the manufacture of caustic potash is identical with the one he recommends. He was the first to prove by sublimation that cinnabar was a compound of sulphur and mercury. He understood perfectly the preparation of acetate of copper, of arsenic, of oxide of lead. The process of refining metals was also familiar to him. He gives the composition of gunpowder,—an invention also attributed to Friar Bacon, but unquestionably due to the Arabs. The idle legends attaching to his name, which have ascribed to him supernatural powers derived from an intercourse with demons, are a part of the homage that mediæval credulity was accustomed to pay to superior intelligence. His life, devoted to science, was as exemplary in its character, in an age of ecclesiastical corruption, as his talents were great and his deeds meritorious. His mathematical knowledge and his mechanical skill were the marvel of his contemporaries. The curious automaton that he constructed, which could open doors and utter guttural sounds, was broken to pieces by St. Thomas Aquinas, who had previously satisfied himself of its magical origin and diabolical character.
Robert Grossetête, Bishop of Lincoln, eminent alike in scientific attainments and theological controversy, is one of the prominent and interesting characters of English mediæval history. An accomplished scholar, he was profoundly versed in all the learning of his time. Anticipating Wyclif by more than a century, he was not afraid to criticise publicly the abuses of the Papacy, to defy its mandates, and to advocate the exercise of individual judgment in ecclesiastical matters. In these daring innovations we obtain the first glimpse of the audacious spirit which animated the founders of the English Reformation. He resisted successfully the presentation of Italian prelates to the vacant benefices of England, a prerogative hitherto exercised by the See of Rome, almost without remonstrance. He elevated the standard of scholarship at Oxford by introducing the methods of examination which obtained in the University of Paris, at that time the first institution of learning in Christian Europe. Although of distinguished rank in the Roman Catholic hierarchy, the unconcealed exultation of the Pope at his decease is a suggestive indication of the broadness of his views, and of the danger to the cause of ecclesiastical supremacy incurred by the extent of his knowledge, the boldness of his sentiments, and the unchecked propagation of his heretical doctrines.
But the greatest of this trio of illustrious names, in both renown and influence, is that of Roger Bacon. Born in 1214, he was early distinguished for his extraordinary abilities. He studied at Oxford and Paris, mastered without difficulty the sciences as taught at those two universities, and, unfortunately for himself, adopted the habit of the Franciscan Order. His inclinations, little in accordance with the maxims of his profession, impelled him to the investigation of natural phenomena. He seems to have had well-defined notions of many practical devices which have contributed largely to the triumphs of modern civilization. He regarded experiment and demonstration as the only rational method of arriving at philosophical truth. A mind endowed with remarkable versatility, a spirit of indomitable perseverance, acquired for him an acquaintance with languages unexampled in his age. In addition to being thoroughly conversant with the classics, Hebrew and Arabic, generally unknown in the thirteenth century except to the Jew and the Saracen, were as familiar to Bacon as the accents of his mother tongue. It is said that he devoted forty consecutive years to the study of science. He expended for rare books and for the apparatus necessary for its researches the sum of two thousand pounds sterling, an amount corresponding to seventy-five thousand dollars of our money. In his writings, he especially recommends the study of mathematics as the most potent instrument of mental culture, the only key which can unlock the secrets of Nature. His erudition embraced the most recondite branches of learning, and some of his suggestions viewed in connection with subsequent discoveries almost seem prompted by supernatural inspiration. He recognized the necessity for the reform of the calendar, and applied to Pope Clement IV. for permission to rectify its errors, but the latter refused. He declared a thorough knowledge of optics to be indispensable for the construction of astronomical instruments. After the perusal of his writings, a doubt can hardly be entertained that he was the inventor of spectacles,—whose idea he obtained from Al-Hazen,—and that he also understood the adjustment of the lenses in the telescope. He explained the phenomena of the rainbow as due to refraction. The power of magnifying-glasses he correctly states to vary with the size of the angle under which the object is seen. He gives the ingredients and describes the effects of gunpowder, a discovery in which he was, however, anticipated by Albertus Magnus. He discourses on the possibilities of inventions similar to the steam-engine, the balloon, and the application of electricity, obscure, it is true, yet with an accuracy of perception that seems incredible, and which cannot be questioned without denying the authenticity of his works. He apparently understood the theory of the suspension-bridge. He refers to the inflammable product obtained by the sublimation of organic matter, probably an allusion to hydrogen. The properties of carbonic acid gas, unfavorable to combustion and fatal to animal life, he mentions in terms whose meaning cannot be misunderstood. He entertained the ancient idea of the compound nature of metals, and declares that, in order to effect their transmutation, a reduction to their primary elements is an essential requisite to success. He explains their artificial coloration, a trick very popular with charlatans, who passed off inferior metals subjected to processes that changed their appearance for silver and gold. The latter metal he asserts to be perfect, because in its formation the operations of countless ages have been completed, and similar processes must be devised by man before he can hope to enter into competition with Nature. In addition to his proficiency in mathematics and chemistry, Bacon was a learned astronomer and a physician. He also constructed automatons, which brought down upon his head the censures of the Church and the enmity of the ignorant. Accused of magic, although he wrote a treatise against it, fanaticism and hatred sentenced him to imprisonment and anathematized his works. After ten years of confinement in a dungeon, he was liberated, only to die with the first return of the blessings of freedom. The intolerant spirit of the age that condemned him is epitomized in a sentence taken from a chapter in which he deplores the irrational bigotry that obstructs the progress of scientific investigation, “Animus ignorans veritatem sustinere non potest.” The versatility of his talents was only surpassed by the audacity with which he attacked and the success with which he controverted the absurd prejudices of his epoch. His name, synonymous with progress, stands forth in prominent contrast with the intellectual abasement and unquestioning credulity with which he was surrounded. His prophetic foresight, while it provoked the ridicule of the thirteenth century, commands alike the respect and astonishment of ours. Like every innovator, he experienced the penalties of superior genius,—persecution, contumely, deprivation of liberty. Among the representative scholars of the Middle Ages, he deserves pre-eminent celebrity as a bold and original exponent of experimental philosophy and scientific thought.
Although unappreciated by his contemporaries, Roger Bacon found a host of imitators during the next three centuries. Members of every rank and profession embraced the study of alchemy. The clerical order included the larger number; the secrecy of the cloister was made subservient to the purposes of magic; and the formulas of the laboratory claimed far more attention than the accomplishment of penance or the ceremonies of devotion. It was even alleged that Pope John XXII. found time at Avignon to engage in a fruitless search for the philosopher’s stone. From these illusory occupations were, as already remarked, occasionally derived discoveries of great practical value. The benefits resulting from the exercise of the spirit of inquiry and the vigorous employment of the intellectual faculties were of even greater consequence to the growth of civilization and the future welfare of mankind.