It is no wonder that his contemporaries spoke of him as the _Doctor centum artium_--the teacher of a hundred arts--for there was practically no branch of scientific knowledge in his time in which he was not expert. Scientific visitors to Rome always considered it one of the privileges of their stay in the papal city to have the opportunity to meet Father Kircher, and it was thought a very great honor to be shown through his museum by himself. Of course, it is difficult for present-day scientists to imagine a man exhausting the whole round of science in this way. Many who have read but little more than the titles of Father Kircher's many books are accordingly prone to speak of him as a mine of information, but without any {126} proper critical judgment. He has succeeded, according to them, in heaping together an immense amount of information, but it is of the most disparate value. There is no doubt that he took account of many things in science that are manifestly absurd. Astrology, for instance, had not, in his time, gone out of fashion entirely, and he refers many events in men's lives to the influence of the stars. He even made rules for astrological predictions, and his astronomical machine for exhibiting the motions of the stars was also meant to be helpful in the construction of astrological tables. It must not be forgotten, however, that in his time the best astronomers, like Tycho Brahe and even Kepler, had not entirely given up the idea of the influence of the stars over man's destiny. As regards other sciences, there are details of information that may appear quite as superstitious as the belief in astrology. Kircher, for instance, accepted the idea of the possibility of the transmutation of metals. It is to be said, though, that all mankind were convinced of this possibility, and indeed not entirely without reason. All during the nineteenth century scientists believed very firmly in the absolute independence of chemical elements and their utter non-interchangeability. As the result of recent discoveries, however, in which one element has apparently been observed giving rise to another, much of this doctrine has come to be considered as improbable, and now the idea of possible transmutation of {127} metals and other chemical elements into one another appears not so absurd as it was half a century ago. Any one who will take up a text-book of science of a century ago will find in it many glaring absurdities. It will seem almost impossible that a scientific thinker, in his right senses, could have accepted some of the propositions that are calmly set down as absolute truths. Every generation has made itself ridiculous by knowing many things "that are not so," and even ours is no exception. Father Kircher was not outside this rule, though he was ahead of his generation in the critical faculty that enabled him to eliminate many falsities and to illuminate half-truths in the science of his day.