All these mirrors I find also in the Optics of Vitello, who wrote in the middle of the thirteenth century, in Italy, a country which was at that time almost the only one where the arts flourished[190]. That author has, indeed, borrowed a great deal from Alhazen, though there are many things of his own, and he gives an account of some experiments on the refracting power of glass; but he never, as far as I have observed, mentions glass mirrors. Whether Jordanus Nemorarius, or Nemoratius, who also wrote, in the thirteenth century, a book _De Speculorum Natura_, makes mention of them, I do not know, because I have never had an opportunity of seeing that work. I am of opinion it was never printed. It is in the thirteenth century, that I find the first undoubted mention of glass mirrors covered at the back with tin or lead. Johannes Peckham, or Peccam, an English Franciscan monk, who taught at Oxford, Paris, and Rome, and who died in 1292, wrote about the year 1279 a treatise of optics, which was once printed, with the title of Johannis Pisani Perspectiva Communis[191]. In this work, besides mirrors made of iron, steel, and polished marble, the author not only speaks often of glass mirrors, but says also that they were covered on the back with lead, and that no image was reflected when the lead was scraped off. Vincentius Bellovacensis[192] speaks in a manner still clearer, for he tells us that lead was poured over the glass plate while hot. To the same century also belong the concurrent testimonies of Raimundus Lullius[193], Roger Bacon[194], Antonius di Padua[195], and Nicephorus Gregoras[196], who died after the year 1360[197]. That this invention cannot be much older we have reason to conclude, because glass mirrors were extremely scarce in France even in the fourteenth century, while mirrors of metal were in common use; and we are told that the mirror of Anne de Bretagne, consort of Louis XII., was of the latter kind[198]. Metal mirrors also were made and employed in Persia and the East, where indeed ancient usages continued longest, and glass mirrors were not known there till the commencement of the European trade with these remote regions. The former are still preferred in those countries, because they are not so liable to break, and can be preserved better in a dry hot climate than the amalgam of the latter.