It is not surprising for those who know of Albert's work, to find that his pupil Roger Bacon defined the limits of chemistry very accurately and showed that he understood exactly what the subject and methods of investigation must be, in order that advance should be made in it. Of chemistry he speaks in his "Opus Tertium" in the following words: "There is a science which treats of the generation of things from their elements and of all inanimate things, as of the elements and liquids, simple and compound, common stones, gems and marble, gold and other metals, sulphur, salts, pigments, lapis lazuli, minium and other colors, oils, bitumen, and infinite more of which we find nothing in the books of Aristotle; nor are the natural philosophers nor any of the Latins acquainted with these things." In physics Albertus Magnus was, if possible, more advanced {47} and progressive even than in chemistry. His knowledge in the physical sciences was not merely speculative, but partook to a great degree of the nature of what we now call applied science. Humboldt, the distinguished German natural philosopher of the beginning of the Nineteenth Century, who was undoubtedly the most important leader in scientific thought in his time and whose own work was great enough to have an enduring influence in spite of the immense progress of the Nineteenth Century, has summed up Albert's work and given the headings under which his scientific research must be considered. He says: "Albertus Magnus was equally active and influential in promoting the study of natural science and of the Aristotelian philosophy. His works contain some exceedingly acute remarks on the organic structure and physiology of plants. One of his works bearing the title of 'Liber Cosmographicus de Natura Locorum,' is a species of physical geography. I have found in it considerations on the dependence of temperature concurrently on latitude and elevation, and on the effect of different angles of incidence of the sun's rays in heating the ground, _which have excited my surprise_."