It is a little bit hard in our time for most people to understand just how such a development of thoroughly scientific chemical notions, with investigations for their practical application, should have come before the end of the Middle Ages. This difficulty of understanding, however, we are coming to realize in recent years, is entirely due to our ignorance of the period. We have known little or nothing about the science of the Middle Ages, because it was hidden away in rare old books, in rather difficult Latin, not easy to get at, and still less easy to understand always, and we have been prone to conclude that since we knew nothing about it, there must have been nothing. Just inasmuch as we have learned something definite about the medieval scholars, our admiration has increased. Professor Clifford Allbutt, the Regius Professor of Medicine at the University of Cambridge, in his Harveian Oration, delivered before the Royal College of Physicians in 1900, on "Science and Medieval Thought" (London, 1901), declared that "the schoolmen, in digging for treasure, cultivated the field of knowledge even for Galileo and Harvey, for Newton and Darwin." He might have added that they had laid foundations in all our modern sciences, in chemistry quite as well as in astronomy, physiology, and the medical sciences, in mathematics and botany. In chemistry the advances made during the thirteenth, fourteenth, and fifteenth centuries were, perhaps, even more noteworthy than those in any other department of science. Albertus Magnus, who taught at Paris, wrote no less than sixteen treatises on chemical subjects, and, notwithstanding the fact that he was a theologian as well as a scientist, and that his printed works fill some _fifteen folio volumes_, he somehow found the time to make many observations for himself, and performed numberless experiments in order to clear up doubts. The larger histories of chemistry accord him his proper place, and hail him as a great founder in chemistry, and a pioneer in original investigation. Even St. Thomas of Aquin, much as he was occupied with theology and philosophy, found some time to devote to chemical questions. After all, this is only what might have been expected of the favorite pupil of Albertus Magnus. Three treatises on chemical subjects from Aquinas' pen have been preserved for us, and it is to him that we are said to owe the use, in the Western world at least, of the word amalgam, which he first employed in describing various chemical methods of metallic combination with mercury that were discovered in the search for the genuine transmutation of metals.