From an attentive perusal of his works, many of which have been printed, it will be seen that Bacon was a great linguist, being familiar with Latin, Greek, Hebrew, and Arabic; and that he had perused the most important books at that time existing in all these languages. He was also a grammarian; he was well versed in the theory and practice of perspective; he understood the use of convex and concave glasses, and the art of making them. The camera obscura, burning-glasses, and the powers of the telescope, were known to him. He was well versed in geography and astronomy. He knew the great error in the Julian calendar, assigned the cause, and proposed the remedy. He understood chronology well; he was a skilful physician, and an able mathematician, logician, metaphysician, and theologist; but it is as a chemist that he claims our attention here. The following is a list of his chemical writings, as given by Gmelin, the whole of which I have never had an opportunity of seeing: 1. Speculum Alchymiæ.[26] 2. Epistola de Secretis Operibus Artis et Naturæ et de Nullitate Magiæ. 3. De Mirabili Potestate Artis et Naturæ. 4. Medulla Alchymiæ. 5. De Arte Chemiæ. 6. Breviorium Alchymiæ. 7. Documenta Alchymiæ. 8. De Alchymistarum Artibus. 9. De Secretis. 10. De Rebus Metallicis. 11. De Sculpturis Lapidum. 12. De Philosophorum Lapide. 13. Opus Majus, _or_ Alchymia Major. 14. Breviarium de Dono Dei. 15. Verbum abbreviatum de Leone Viridi. 16. Secretum Secretorum. 17. Tractatus Trium Verborum. 18. Speculum Secretorum. [26] This tract and the next, which is of considerable length, will be found in Mangetus’s Bibliotheca Chemica Curiosa, i. 613. A number of these were collected together, and published at Frankfort in 1603, under the title of “Rogeri Baconis Angli de Arte Chemiæ Scripta,” in a small duodecimo volume. The Opus Majus was published in London in 1733, by Dr. Jebb, in a folio volume. Several of his tracts still continue in manuscript in the Harleian and Bodleian libraries at Oxford. He considered the metals as compound of mercury and sulphur. Gmelin affirms that he was aware of the peculiar nature of manganese, and that he was acquainted with bismuth; but after perusing the whole of the Speculum Alchymiæ, the third chapter of which he quotes as containing the facts on which he founds his opinion, I cannot find any certain allusion either to manganese or bismuth. The term _magnesia_ indeed occurs, but nothing is said respecting its nature: and long after the time of Paracelsus, bismuth (_bisematum_) was considered as an impure kind of _lead_. That he was acquainted with the composition and properties of _gunpowder_ admits of no doubt. In the sixth chapter of his epistle De Secretis Operibus Artis et Naturæ et de Nullitate Magiæ, the following passage occurs: