THE CHEMISTRY OF TO-DAY. 591 



THE CHEMISTRY OF TO-DAY. 



By lEA EEMSEN, 



PEOFESSOE OF COEIUSTEY IN JOHNS HOPKINS UNIVEESITT. 



SOME years ago, in the course of a conversation witli an emi- 

 nent 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 defi- 

 nition—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 cer- 

 tainly 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 con- 

 vey. To illustrate what I mean by this, let me take an example or 

 two. Suppose a chemist is given a piece of marble. On exam- 

 ining 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- 



