Dr. Whewell says that Roger Bacon's Opus Majus is "the encyclopedia and Novam Organon of the Thirteenth Century, a work equally wonderful with regard to its general scheme and to the special treatises with which the outlines of the plans are filled up. The professed object of the work is to urge the necessity of a reform in the mode of philosophizing, to set forth the reasons why knowledge had not made a greater progress, to draw back attention to the sources of knowledge which had been unwisely neglected, to discover other sources which were yet almost untouched, and to animate men in the undertaking by a prospect of the vast advantages which it offered. In the development of this plan all the leading portions of science are expanded in the most complete shape which they had at that time assumed; and improvements of a very wide and striking kind are proposed in some of the principal branches of study. Even if the work had no leading purposes it would have been highly valuable as a treasure of the most solid knowledge and soundest speculations of the time; even if it had contained no such details it would have been a work most remarkable for its general views and scope." It is only what might have been expected, however, from {46} Roger Bacon's training that he should have made great progress in the physical sciences. At the University of Paris his favorite teacher was Albertus Magnus, who was himself deeply interested in all the physical sciences, though he was more concerned with the study of chemical problems than of the practical questions which were to occupy his greatest pupil. There is no doubt at all that Albertus Magnus accomplished a great amount of experimental work in chemistry and had made a large series of actual observations. He was a theologian as well as a philosopher and a scientist. Some idea of the immense industry of the man can be obtained from the fact that his complete works as published consist of some twenty large folio volumes, each one of which contains on the average at least 500,000 words. Among these works are many treatises relating to chemistry. The titles of some of them will serve to show how explicit was Albert in his consideration of various chemical subjects. He has treatises concerning Metals and Minerals; concerning Alchemy; A Treatise on the Secret of Chemistry; A Concordance, that is a Collection of observations from many sources with regard to the Philosopher's Stone; A Brief Compend on the Origin of the Metals; A Treatise on Compounds; most of these are to be found in his works under the general heading "Theatrum Chemicum."