the apartments, that by numerous fires on the blazing hearth they might counteract the dangerous chill which threatened to seize on their limbs. [169] ROGER BACON. Roger Bacon, of whom extraordinary stories of magic have been told, and who was about twenty years younger than Albertus, was one of the rarest geniuses that have existed on earth. He was a Franciscan friar. He wrote grammars of the Latin, Greek and Hebrew languages. He was profound in the science of optics. He explained the nature of burning-glasses, and of glasses which magnify and diminish, the microscope and the telescope. He discovered the composition of gunpowder. He ascertained the true length of the solar year; and his theory was afterwards brought into general use, but upon a narrow scale, by Pope Gregory XIII, nearly three hundred years after his death. [170] But for all these discoveries he underwent a series of the most bitter persecutions. It was imputed to him by the superiors of his order that the improvements he suggested in natural philosophy were the effects of magic, and were suggested to him through an intercourse with infernal spirits. They forbade him to communicate any of his speculations. They wasted his frame with rigorous fasting, often restricting him to a diet of bread and water, and prohibited all strangers to have access to him. Yet he went on indefatigably in pursuit of the secrets of nature. [171] At length Clement IV, to whom he appealed, procured him a considerable degree of liberty. But, after the death of that pontiff, he was again put under confinement, and continued in that state for a further period of ten years. He was liberated but a short time before his death.