When we read of the curriculum of the European Universities during the Middle Ages we are inclined to think that certain classical studies, literature and languages, music, and mathematics, were almost the only subjects taught that had reasonable foundations. The natural sciences are generally supposed to have been in their infancy (as of course they were) when not purely fanciful, arbitrary, and grotesquely erroneous. But now and then side-light is thrown into some obscure corner and the existence of correct knowledge discovered among much that is doubtful or wrong.
A most interesting instance exists in an Irish Treatise on Astronomy now in the Library of the Royal Irish Academy, and which was translated into English by Mr. J. J. O'Farrelly in 1893. It was written about the year 1400, certainly not later, and is derived from the works of Messahalah, an Arabian Jew who lived between a. d. 754 and 833. Twelve of the thirty-nine chapters are not contained in the Latin versions of Messahalah's treatises from which the Gaelic translation was derived; their origin is unknown, but they probably came from other Arabian sources, or they may have been in part the results of the observations and studies of the Irish writer himself.
The treatise is based upon the Ptolemaic theory of the Solar System. It is remarkable that Ptolemy did not accept the Pythagorean System, which placed the sun as the central body instead of the earth, for the teachings of Pythagoras had been widely diffused in the time of Ptolemy. The result of his refusal to work on the correct system of the great Initiate, Pythagoras, was that the students of astronomy were misled and held back from the knowledge of the true relationship of the sun and the earth for many centuries, and much bitterness was aroused.
The Irish MS. carefully explains the globular shape of the earth, and gives its true, approximate diameter, 8000 miles; the real causes of the phases of the moon, its eclipses, and the eclipses of the sun, are stated; the reason why the sun rises earlier if you travel eastward and later if you go westward is properly explained; the writer points out that the moon, like the planets, has no light of its own but reflects that of the sun. He also touches upon physical geography and geology. He gives, though with some hesitation, the true explanation of the rising of the Nile. His remarks about the wearing down of the mountains by the action of rivers, and upon the origin of fossil shells agree remarkably with the principles of modern geology. Yet, hundreds of years afterwards, geology had to fight for its life against the entrenched strongholds of learned ignorance and prejudice which went so far as to say that the fossils were artfully placed in the rocks by the Devil in order to try the faith of the pious in the literal accuracy of the Genesis account of creation in six days.
But the most curious thing in the whole treatise is a statement which shows the possession of information upon a subject of which it is generally believed that nothing was or could be known before the invention of the astronomical telescope by Galileo in 1609 — two hundred years later! This is that when the planets Venus and Mercury "are twelve degrees proceeding westward of the sun they are horned like the new moon."
One of the strongest arguments against the true theory (Pythagorean or Copernican) of the solar system was that Venus failed to show the crescent or horned phase like the moon as it should do. As the phases of Venus cannot be detected without optical aid, and as the critics possessed nothing of the kind, they had some show of reason in not accepting the truth; but when Galileo turned his "optic tube" upon the Planet of Love it was immediately seen that it did pass through exactly the phases of crescent, half-moon, and full-moon, that ought to be seen.
How then comes it that the unknown Irish writer was able two hundred years before Galileo, to write quite confidently of the crescent phase of Venus, and also of Mercury, a much more difficult object to distinguish? Perhaps the answer to this will be forthcoming when it is explained how it was that the ancient Assyrians represented Bel, the Assyrian Jupiter, with four star-tipped wings, and the god corresponding to Saturn standing within a ring, as Proctor, the famous English astronomer, pointed out in Our Place Among Infinities, unless they knew by telescopic observation that Jupiter had four large moons and that Saturn was surrounded by a wonderful ring!
This is another instance of the debt owing to that remarkable Arabian civilization and culture which flourished so brilliantly in Spain and the nearer Orient, at a time when the intellect of Europe proper had not yet awakened. How dark those rightly termed Dark Ages were when the Arabian Jew Messahalah wrote in the ninth century, can only be appreciated by those who have given the time and energy necessary to understand it. When this fifteenth century Irish writer composed his treatise, the mind of Europe had already begun to stir; the priceless treasures of Greek knowledge had been lately brought to Europe and had quickened the sluggish and stupefied thought to unwonted activity, while the dullest could see the parallels in the Greek writers with the philosophy and science of the Jewish-Arabian culture. Just as the Greek intellect had expressed itself in science, philosophy, and mathematics, in Pythagoras, Plato, Eratosthenes, and Euclid, who themselves were to a large degree indebted to Asia, so the Saracens who studied and absorbed these writers, stamped their own productions with their own native genius, and in turn handed on to the European the Grecian thought, based as it was on Asiatic (Babylonian, Syrian, Egyptian) achievements. What a curious and interesting reflexion it is, that the theoretic and philosophical systems of the Egyptian Babylonian priest-scientists should have wandered from their native soils to Ionia, Peninsular Greece, and Magna Graecia; then to return to their native continent, and after greatly aiding to mold and soften the manners of the Men of the Desert, to be carried to Spain, and from Spain to meet again in the European Universities the other branch of the same stream of Asiatic learning flowing from Constantinople. Truly, so far as European history is concerned, no more fascinating page exists than this period of renaissance. And, sad to say, no period has been treated so meagerly by historians.