As I go over this manuscript for the last time just before going to press, there comes the announcement that Sir William Ramsay has probably solved the problem of the transmutation of metals. He has shown apparently that lithium, when acted upon by radium emanations, changes to some extent to copper. It is true that the change is only in small quantities, and that there is no question as yet of any commercial value to the process; but we all know that it is by such small scientific announcements as this that the entering wedges of large industrial processes are introduced. The fact that this announcement should have been made before the British Association for the Advancement of Science and by a thoroughly conservative English chemist, probably settles forever the question of the transmutation of metals, in the way that the people of the Middle Ages looked at the problem rather than as the intervening centuries did. The old medieval thinkers, then, were only ridiculous to a few generations of nineteenth century scientists who, because they knew a little more about certain details in science than preceding generations had done, thought that they knew all that there was to be known about this immense subject, and made fun of thinkers quite as great as themselves in preceding centuries. At the beginning of the twentieth century, instead of making ourselves ludicrous by raising a laugh at the expense of these fellow students in science of the olden time, we should rather feel like congratulating them upon the perspicacity which enabled them to anticipate a great truth with regard to the relationships of chemical elements, especially the metals, to each other. The present-day idea of thinking physicists and chemists is {311} that the seventy odd elements described in our textbooks on chemistry, are not so many essentially independent forms of matter, but are rather examples of one kind of material exhibiting special dynamic energies which it possesses under varying conditions, as yet not well understood. This was exactly the idea that the old scholastic philosophers had of the constitution of matter. They said that matter was composed of two principles, prime matter and form. When this doctrine of theirs is properly elucidated, it proves to be an anticipation of what is most modern in the thoughts of twentieth century physicists. A re-statement of the old-time views would read not unlike many a contribution to a discussion of this subject at an annual meeting of the British or American Associations for the Advancement of Science.