168 



SCIENCE. 



[N. S. Vol. XV. No. 370. 



its dominion over chemical tliought. One 

 danger, however, confronts it— the danger 

 of self-exaggeration, stimulated by over- 

 popularity. Physical chemistry, to acliieve 

 the best results, has need of data drawn 

 from other lines of chemical research; if 

 they are neglected, it in turn vsdll suffer. 

 Even now too large a proportion of its 

 votaries are working in one field ; that is, on 

 questions grooving out of the current theory 

 of solutions, and other subjects fail to re- 

 ceive the attention which they deserve. 

 This state of affairs, this lack of proportion, 

 is doubtless only temporary, for towards 

 physical chemistry all chemical theories 

 converge, and no phase of it, therefore, can 

 long escape consideration. The very nature 

 of physical chemistry implies the prohibi- 

 tion of narrowness ; broad conceptions and 

 deep insight are essential to its being. 



When we consider the complex influences, 

 the varied demands, through which chemis- 

 try has developed hitherto, we can only 

 wonder at the outcome. Under the circum- 

 stances, a symmetrical growth was impos- 

 sible; the marvel is that so much could 

 have been accomplished. Out of unorgan- 

 ized, uncoordinated, individual efforts a 

 true science has come into existence, equal 

 in dignity to any other within the domain 

 of learning. All science is defective, but in 

 its very imperfections Ave find its greatest 

 charm. Through them alone effort be- 

 comes possible; a wise discontent on our 

 part is the first condition for progress. If 

 all were known, research would come to an 

 end; nothing could arouse our curiosity; 

 the human mind would atrophy for want 

 of exercise. The search for truth is better 

 than the truth itself— if I may be allowed 

 thus to paraphrase the well-known words of 

 Lessing. In what direction, then, shall we 

 pursue our search, and with what promise 

 for the future? What are the needs of 

 chemistry ? 



Pardon me, now, if I apparently indulge 



in commonplace; if I cite some considera- 

 tions of almost alphabetic simplicity. Fun- 

 damental principles lie so close to our eyes 

 that they are easily overlooked; and from 

 negligence of that kind, misdirected effort 

 may follow. We must review our lessons 

 sometimes in order to make sure of what 

 we really know. In the first place it is well 

 to bear in mind that chemistry and physics 

 are not sharply distinct ; that they are two 

 parts of the same great body of truth ; and 

 that neither can be studied to the best ad- 

 vantage vnthout aid from the other. Both 

 rest upon the same two basic doctrines — the 

 conservation of energy and the persistence 

 of matter — conceptions which supplement 

 each other and which give our work its 

 philosophical validity. 



If we try to consider chemistry by itself, 

 to conceive of it as an independent branch 

 of learning, we shall find that it has but 

 one fundamental problem, namely, the 

 study of chemical reactions. From certain 

 kinds of matter certain other kinds are pro- 

 duced; and we merely investigate the laws 

 which govern the transformations. If we 

 prepare new compounds, we discover that 

 such and such reactions are possible, and 

 we describe their products. If we are in- 

 terested in chemical equilibrium, we seek 

 to determine the limits between which a 

 given change can occur. Even our notions 

 of chemical structure and atomic linking 

 are but devices through which reactions and 

 their products may be coordinated. In 

 every case the reaction is the ultimate ob- 

 ject of purely chemical research, and we 

 try to ascertain its laws. Beyond this we 

 enter the realm of physics; we describe 

 each kind of matter in thermal, optical, 

 electrical, mechanical and gravitational 

 terms, and we discuss the phenomena of 

 chemical change in similar phraseology. 



Let us take, for example, any reaction 

 whatever, and see what its complete investi- 

 gation signifies. At once the problem will 



