258 Mr. M. M. Pattison Muir on Chemical Classification. 



confronting tliem. I liave almost ignored this question in 

 the preceding paragraphs of this paper. Our knowledge of 

 chemical action considered as a form of energy, is as yet 

 almost nil. For the purposes of study it seems better to keep 

 separate the questions, What is the structure of this or that 

 body ? and Why is the structure as it is ? The first question 

 relates to chemical statics, the second to chemical kinetics. 

 The greater part of the labours of chemists has hitherto been 

 dcYoted to attempting an answer to the first question. They 

 have made some progress in the attempt ; but there remains 

 much to be done. When they shall have fully answered both 

 questions, the science of chemistry will be complete. But that 

 iclien is a long time off. ^Nevertheless, of each question it 

 may be said, in the words of Lothar Meyer, " dass ihre Er- 

 forschung nicht nur moglich ist, sondern audi cine ausseror- 

 dentlich dankbare Aufgabe fiir den menschlichen Forscher- 

 geist bildet " *. 



28. I have thus endeavoured to give some kind of answer 

 to the questions proposed at the close of paragraph 11, con- 

 cerning the utility of that system of classification which is 

 mainly founded upon the valency of the elementary atoms. 

 This system does not, as yet, give us ^^ a means for definitely 

 settling the characteristics of each class ;" it does not enable 

 us, as yet, "to mark off class from class ;" we cannot, as yet, 

 " by its aid, correlate the leading characteristics of each class 

 with the valency of the elementary atoms;" nor can we, as 

 yet, " show a clear connexion between valency and chemico- 

 physical properties of elements and compounds." A classifi- 

 cation which might now be founded upon the valency of the 

 elementary atoms would not fulfil the tests of a good system, 

 as laid down in the first paragraph of the present paper. 

 I'^evertheless I think that I have succeeded in showing (or 

 if I have failed, I think that the failure is due to want of 

 clearness or of knowledge on my part, not to a deficiency in 

 the facts themselves) that in the theory of valency, and in 

 those subsidiary theories which are outcomes from it, we 

 have a principle which is guiding research in drrections in 

 which valuable results have been already obtained, and in 

 which we may confidently hope for yet better results in the 

 future. I hope I have succeeded in establishing a large pro- 

 bability in favour of the belief that this principle will be one 

 of the main foundations upon which a complete system of 

 chemical classification will some day be raised ; and at the 

 same time I trust I have not altogether failed in representing 

 * Die mo(lor7ten Thcorien^ 2ucl cd. p. 140, 



