Mr. M. M. Pattison Muir on Chemical Classification. 271 



facts. But to eiideavonr to mend this mistake by declaring 

 that science has no need of hypotheses appears to me to Le 

 but fallings if possible, into a worse error. 



34. I have thus endeayoured shortly to trace the evolution 

 of chemical theory in the past, and to indicate a few of the 

 main lines along which, as it seems to me, it must proceed in 

 the more or less immediate future. Although I have entitled 

 tliis paper "On Chemical Classification," yet I have made no 

 attempt at a system of classification : the time for such an 

 attempt is yet, I believe, a long v/ay oif. We have, it is 

 true, various systems, each, it may be, good in itself, and 

 useful for certain limited purposes. But it is only when we 

 shall have attained to a much wider knowledge of the con- 

 nexions existing between composition and properties of 

 chemical bodies that any attempt at a large scheme of clas- 

 sification likely to prove of lasting value need be made. 



The three main lines of research (see par. 29) indicated in 

 the foregoing paragraphs even now blend into one another ; 

 yvQ cannot keep them altogether separate, if vre would. The 

 barriers betvveen them are, of course, artificial, and merely 

 set up as aids to research. Many subsidiary problems, not 

 strictly included within any of these general questions, already 

 present themselves, and will, in all probability, increase in 

 number as investigation progresses. 



A considerable number of exceptional phenomena are even 

 now known, Avhich are scarcely touched by any of our 

 theories. Such, for instance, is the phenomenon of allo- 

 tropism. We seem to have a vague idea of some kind con- 

 nected with this word ; but if a student were asked in an 

 examination, " What are allotropic states ?" and if he were to 

 adopt the words of Prof. Stanley Jevons, and reply, " Curious 

 states, which chemists conveniently dispose of by calling them 

 allotropic, a term freely used w^hen they are puzzled to know 

 what has happened"*, he might be plucked; but on the 

 question of allotropism he would be scarcely less ignorant 

 than his examiner. 



Exceptional phenomena form the nuclei around which re- 

 searches, rich in fruitful v>'ork, must congregate. The science 

 of Chemistry has made great advances in recent years ; but it 

 is now only entering on the exact stage of its history. Before 

 that history can be completed much labour of head and hands 

 is required ; but it will be richly rewarded. " Yiel Arbeit der 

 Geister wie der Hande ist erforderlich,^aber sie wird reichlich 

 belohnt werden" t- 



* ' Principles of Science/ vol. ii. p. 341. 

 t Die iiwdcynen Tlieonhi, 2ud. edit. p. ool , 



