8 Dr. E. J. Mills on Isomerism, 



the necessity of continual support from fresh subordinate theo- 

 ries. The theory of atomicities, as usually accepted, failed to 

 account for such a pair of combinations as 



I CI I CI 3 ; 



and the doctrine of " molecular union " was promulgated as sol- 

 ving the difficulty. On the other hand,, the precisely analogous 

 case, 



(C 3 H 5 )Br (C 3 H 5 )Br 3 , 



has been explained on the principle of self- saturation (in the 

 carbon) . Such methods of treatment, however admirable from 

 an sesthetical point of view, can hardly be said to present logical 

 grounds for acceptance. 



The various phases of the theory of isomerism cannot be con- 

 templated with satisfaction by those philosophers who do not 

 hold atomic views. It has indeed been urged that there is no 

 proof of the existence of atoms*, that the entire analogy of 

 nature is against a doctrine of indivisibles, that an absolute limit 

 of any kind is inconceivable and beset with contradictions which 

 cannot be resolved f. Means, however, exist for the formation 

 of a theory which is not embarrassed by corpuscular notions ; 

 and early writers on isomerism would doubtless have availed 

 themselves of these means had not the popular scientific mate- 

 rialism led them to mistake the true nature of the problem. For 

 the question relates to force {, not to matter; and to that par- 

 ticular aspect of force of which the theory of polarity takes cog- 

 nizance. The polar doctrine, enunciated in its most primitive 

 and philosophical form by Herakleitus§, has not been allowed 

 to fall into obscurity by modern authors. It has been expounded 

 in the concrete chemical sense by Davy ||, Avogadro% Berzelius, 

 Graham**, Brodieft, and others. According to this view, matter 

 undergoing chemical change is polarized ; that is, a part or parts 

 of a given mass are rendered antagonistic to the remaining part 

 or parts. Whether this antagonisui remains permanent or not 

 after the reaction has terminated cannot yet be decided for every 

 case; it is sufficient to know that it does remain constant in 



* " Utrum vero partes illse distinctse et nondum divisse per vires naturae 

 dividi et ab invicem separari possint, incertum est." — Newton, Principia, 

 vol. iii. p. 358 (2nd edit. 1713). 



f Bampton Lectures, 1858, pp. 58, 59. 



i Compare Chem. Soc. Journ. [2] vol. iii. p. 329. 



§ " Der Ausdruck 6$6$ avco Kara bedeutet uns daher nur das Umschla- 

 gen der Gegensatze ineinander iiberhaupt." — Lassalle, Die Philosophic He- 

 rakleitos des Dunklen, vol. ii. p. 250. 



|| Phil. Trans. 1807, p. .39. f Journ. de Phys. 1809, p. 147. 



** Elements, 1842, p. 204. ft Phil. Trans. 1850, p. 759. 



