The scientists of that day were concerned almost solely with astrology and alchemy, and owing to the superstition then so prevalent, all who studied these so-called sciences were liable to be suspected of practising the magic arts.

Roger Bacon was not the man to be turned from the pursuit of knowledge, by any fear of evil consequences that might spring from the ignorance of his fellow-men. Born of a good Somerset family, he was sent to Oxford, where he studied the works of Aristotle, which had been forgotten for centuries, and thus became acquainted with the greatest of the classical scientists. He also took a great interest in mathematics, and was the first to apply this knowledge to the science of astronomy. After some years at Oxford, he went to the University of Paris, returning to Oxford again in 1250. He then entered the Francisan Order, and hence is often called Friar Bacon. Having acquired all the learning of the age, he spent all that he had, and much that he borrowed from friends, in his scientific researches into the secrets of nature. He was especially interested in the science of optics, as being useful to the study of astronomy, and this resulted in the invention of the magnifying glass, but he was greatly hindered by the need of proper apparatus.

Such a man would naturally gather many students around him, and we learn that he was a kindly teacher, and never hesitated to impart his knowledge freely, when his scholars were too poor to make him any payment.

"From my youth up," he writes, "I have laboured at the sciences and tongues. I have sought the friendship of all men among the Latins who had any reputation for knowledge. I have caused youths to be instructed in languages, geometry, arithmetic, the construction of tables and instruments, and many needful things besides."

Returning to Paris, his great gifts brought him many enemies, and he was at last accused of the practice of magic and imprisoned in 1257. He was forbidden all intercourse with the world, and even the privilege of writing was denied him. Then Pope Clement IV. became interested in his work, and it was at the Pope's request that Bacon wrote his Opus Magus, and the manuscript was sent to Rome by the hand  of his favourite pupil, John of London. We do not know how it was received, for Clement died shortly afterward.

This wonderful book sums up the state of knowledge, both in philosophy and science, of the time. Many other books were written by Friar Bacon, some of which have never been translated from the Latin in which all learned books were written in his day, for Latin was still the common language of European scholars.

In his later years Bacon drew up a rectified calendar, invented gunpowder, and was, as Mr. Lecky says, "the greatest natural philosopher of the Middle Ages." It seems strange to us that such a man could believe in astrology and in the philosopher's stone, but Bacon was sufficiently a child of his time to feel the fascination which these idle pursuits had for nearly all the learned men of that day.

Bacon's greatest achievement was his application of new principles to the study of science. He believed that experiment was necessary, and not merely the acceptance of beliefs handed down from ancient philosophers. To his optical and astronomical researches he brought to bear his knowledge of mathematics, in which he had learnt much from the Arabs, who in that day were especially renowned in that science.

Although his work had no great immediate effect, owing to the decay of learning  during the next two centuries, when all the energies of the Church were devoted to preventing schism, his influence during the Renaissance in the sixteenth century was marked, for many of his books were amongst the earliest printed.

Bacon was released from prison in Paris about the year 1267, and for ten years enjoyed his freedom in spite of the attacks of his enemies. In 1278 the chief of the Franciscan Order declared his books to be unorthodox, and kept him in confinement until 1292. Two years later he died at Oxford.