| THE CHEMISTRY OF TO-DAY. |
By IRA REMSEN,
PROFESSOR OF CHEMISTRY IN JOHNS HOPKINS UNIVERSITY.
SOME years ago, in the course of a conversation with an eminent mathematician, I asked in all seriousness whether he could give me a definition of mathematics that would convey to my mind even a faint idea of the object in view in mathematical investigation. He replied, "It is impossible to give such a definition—as impossible as it is in the case of chemistry." "But," said I, "I think I can give a definition of chemistry which would have some value"; and then, with little time to think, I suggested a definition, which elicited this remark: "I could certainly give an equally bald definition of mathematics." I have frequently thought of this subject since, and have wondered whether it is possible to convey to the minds of those who are not chemists a clear idea in regard to the work chemists are doing. The difficulties are great—as great, I suppose, as in the case of mathematics; for chemists are no longer engaged in the study of familiar phenomena, but are dealing with matters which lie far beyond the limits of ordinary observation. Still, I have thought it worth while to make the attempt, and it has seemed to me that I might accomplish my object best by calling attention to a few of the most important discoveries which have recently been made in the field of chemistry, and making such comments upon them as may serve to indicate what relations exist between these discoveries and the science as a whole.
Chemistry may be defined as that branch of science which has to deal with the changes in composition which the various forms of matter undergo. Not only has it to deal with these forms of matter, but also with the changes—that is, the acts involved in passing from one form to another. However bald this definition may appear to those who do not understand the subject, it is full of suggestion to the chemist. A chemist is sometimes spoken of as "one whose business it is to tell what things are made of." I accept this statement as expressing half the truth, but I attach to the words a much deeper meaning than they are intended to convey. To illustrate what I mean by this, let me take an example or two. Suppose a chemist is given a piece of marble. On examining it he finds without much difficulty that it is made of the forms of matter called carbon, oxygen, and calcium. He can also tell without much difficulty in what proportions these substances are present in the marble. He may thus tell what marble is made of. But is that all? May we not ask further what are the sub-
