CHEMISTRY. 



By GEORGE F. BARKER, 



Professor op Physics in the University of Pennsylvania, Philadelphia. 



GENERAL. 



Among the valuable contributions made to chemistry dur- 

 ing the year 1878, we note the address of Professor Kekule, 

 on entering upon the duties of rector of the University of 

 Bonn, upon the scientific position of this science and its fun- 

 damental principles. He defined chemistry, and differentiated 

 it from physics and mechanics, thus: "Chemistry is the sci- 

 ence of the statics and dynamics of atoms; physics, that of 

 the statics and dynamics of molecules; while mechanics con- 

 siders the masses of matter consisting^ of a larsre number of 

 molecules." In opposition to the opinion that theory should 

 be banished from the exact sciences, he regarded it as an act- 

 ual felt necessity of the human mind to classify the endless 

 series of individual facts from general standpoints at pres- 

 ent of a hypothetical nature and that it was precisely the 

 discussion of these hypotheses which often led to the most 

 valuable discoveries. 



Sylvester has communicated to Nature a novel paper on 

 an analogy which he has observed between the valence-con- 

 ceptions of modern chemistry and the theory of modern al- 

 gebraic forms, between atoms and binary quantics. The num- 

 ber of bonds of an atom is the analogue of the number of 

 factors in a binary quantic, a linear form of the latter being 

 regarded as corresponding to a monad atom, a quadratic form 

 to a dyad, a cubic form to a triad, etc. An invariant of a 

 system of binary quantics of various degrees is the analogue 

 of a chemical substance composed of atoms of corresponding 

 valences. A co-variant is the analogue of a compound radi- 

 cal. Every invariant and co-variant is expressible by a graph 

 precisely identical with the Crura. Brown diagram or chemi- 

 cograph. The author believes that in this analogy a ration- 

 al basis for chemical valence may be discovered. 



