Mr. M. M. Pattison Muir on Chemical Classification, 87 



If pushing feeblo analogies too far led Lavoisier astray as 

 regards the constitution of hydrochloric acid and chlorine, a 

 somewhat similar use of analogy led him to true ideas i*egard- 

 ing the constitution of the alkaline earths. 



Lavoisier observed that metals dissolved in acids with efferves- 

 cence, and that bases dissolved without effervescence ; he fur- 

 ther observed that lime and magnesia dissolved in acids without 

 effervescence : hence he inferred that the latter substances are 

 probably compound bodies. \\\ this case Lavoisier put forward 

 his views regarding the constitution of these alkaline earths 

 in the form of an hypothesis only ; the hypothesis was useful 

 as a guide in future work, and was most fruitful of good re- 

 sults. Li the cases of hydrochloric acid and of chlorine, Lavoi- 

 sier put forward what was really an hypothesis, founded on 

 much the same kind of evidence as the hypothesis concerning 

 the nature of lime and magnesia, as an ascertained fact. 

 The false fact retarded the advance of science, and raised 

 many prejudices in the minds of chemists which future in- 

 vestigators found it hard to remove. 



7. The views of Lavoisier concerning the constitution of 

 gaits were developed by Berzelius in the terms of his famous 

 theory of Dualism. 



Starting with the assumption that a salt is formed by the 

 union of an acid with a simple or compound radicle, Ber- 

 zelius represented all salts as built up of two parts held toge- 

 ther by electric foi'ce of some kind. These two pai*ts might 

 consist of two simple elements, or of two radicles themselves 

 built up of almost any conceivable number of elements. How- 

 ever complicated the radicles, Berzelius regarded the salt as 

 consisting of two distinct parts tied together, as it were, by an 

 electric cord, which was sometimes assisted by the intervention 

 of a'third radicle called a copula. The rise of the atomic theory 

 furnished Berzelius with a means for presenting his hypothesis 

 in its most favourable colours. The idea that chemical union 

 is a union between atoms seemed to find its natural outcome 

 in the theory of Berzelius. If atoms combine, why cannot 

 groups of atoms do the same ? Can we avoid regarding a salt 

 as made up of bundles of atoms, these bundles being themselves 

 composed of simpler atoms ? The theory of Dualism appeared 

 to explain the composition of all known compounds ; it was 

 triumphant. 



If we compare the views of Berzelius with those of the 

 predecessors of Lavoisier, we find that while with them 

 function was all, with Berzelius composition was supreme. 

 The alchemists and iatrochemlsts asked, What does this sub- 

 stance do? Berzelius asked, Of what Is this substance com- 



