terms; in the names of the principal "fixed" stars; and in the words "admiral" and "chemise"; the influence of the "Arab" in science, war, and dress. It forms no part of our story to tell how feuds between rival dynasties and rival sects of Islam, becoming more acute as time went on, enabled Christianity to recover lost ground, and, in the capture of Granada in 1492, to put an end to Moorish rule in Spain. Before that event, a knowledge of Greek philosophy had been diffused through Christendom by the translation of the works of Avicenna, Averroes, and other scholars, into Latin. That was about the middle of the twelfth century, when Aristotle, who had been translated into Arabic some three centuries earlier, also appeared in Latin dress. The detachment of any branch of knowledge from theology being a thing undreamed of, the deep reverence in which the Stagirite was held by his Arabian commentators ultimately led to his becoming "suspect" by the Christians, since that which approved itself to the followers of Mohammed must, _ipso facto_, be condemned by the followers of Jesus. Hence came reaction, and recourse to the Scriptures as sole guide to secular as well as sacred knowledge; recourse to a method which, as Hallam says, "had not untied a single knot, or added one unequivocal truth to the domain of philosophy." So far as the scanty records tell (for we may never know how much was suppressed, or fell into oblivion, under ecclesiastical frowns and threats; nor how many thinkers toiled in secret and in dread), none seemed possessed either of courage or desire to supplement the revealed word by examination into things themselves. To supplant it was not dreamed of. But, in the middle of the thirteenth century, one notable exception occurred in the person of Roger Bacon, sometimes called Friar Bacon in virtue of his belonging to the order of Franciscans. He was born in 1214 at Ilchester, in Somerset, whence he afterward removed to Oxford, and thence to Paris. That this remarkable and many-sided man, classic and Arabic scholar, mathematician, and natural philosopher, has not a more recognised place in the annals of science is strange, although it is, perhaps, partly explained by the fact that his writings were not reissued for more than three centuries after his death. He has been credited with a number of inventions, his title to which is however doubtful, although the doubt in nowise impairs the greatness of his name. He shared the current belief in alchemy, but made a number of experiments in chemistry pointing to his knowledge of the properties of the various gases, and of the components of gunpowder. If he did not invent spectacles, or the microscope and telescope, he was skilled in optics, and knew the principles on which those instruments are made, as the following extract from his Opus Majus shows: "We can place transparent bodies in such a form and position between our eyes and