302 TEE POPULAR SCIENCE MONTHLY, 



as imagined by Hobbes, is unquestionable ; but how Mr. Mill could 

 describe that union as chemical, and as analogous to the compound 

 formed like water, by hydrogen and oxygen, is inexplicable if it be 

 remembered that the composition of water was not discovered by 

 Cavendish till 1784 — thirty-five years after the appearance of the 

 " Observations " — and that Chemistiy only passed from the meta- 

 physical to the positive stage with the deposition of phlogiston by 

 Priestley and Lavoisier in the last quarter of the century. The fol- 

 lowing quotations from Hartley himself will confirm this a jyriori ar- 

 gument by showing the real nature of association as figured by him : 



" Upon the whole, it may appear to the Eeader, that the simple Ideas of 

 Sensation must run into Clusters and Combinations, by Association ; and that 

 each of these will, at last, coalesce into one Complex Idea, by the Approach 

 and Commixture of the several compounding Parts.'" 



Xo chemist would describe chemical union as "coalescence," or 

 speak of the new substance produced by the operation of affinity as 

 made up of " clusters and combinations " by the " approach and com- 

 mixture " of parts. As appears still more clearly when Hartley pro- 

 ceeds to explain and illustrate this " coalescence," he had in his mind, 

 as the physical type of his conception, no more " intimate union " than" 

 that combination of difierent kinds of matter called solution : ^ 



"If the Number of simple Ideas which compose the complex one be very 

 great, it may happen that the complex Idea shall not appear to bear any rela- 

 tion to these its compounding Parts, nor to the external Senses upon which the 

 original Sensations, which gave Birth to the compounding Ideas, were impressed. 

 The Peason of this is, that each single Idea is overpowered by the Sum of all 

 the rest, as soon as they are all intimately united together. Thus, in very com- 

 pound Medicines, the several Tastes and Flavors of the separate Ingredients are 

 lost and overpowered by the complex one of the whole Mass : so that this has a 

 Taste and Flavor of its own, Which appears to be simple and original, and like 

 that of a natural Body." ^ 



We should be disposed to describe Hartley's view of mental compo- 

 sition as bearing a similar relation to James Mill's synthesis as New- 

 ton's composition of light to Goethe's theory of colors — as implying 

 some species of union closer than the mechanical and less binding 

 than the chemical. Thomas Brown clearly stated the law. as chemi- 

 cally conceived, in one of his introductory lectures. In mere state- 

 ment James Mill's exposition is no advance upon Brown's, but the law 

 took enormous extensions in his hands, and was applied to the senses, 

 the feelings, memory, classification, language, ratiocination, the will, 

 belief, etc. Something has been added to his synthesis, and a little 

 has been taken from it, but he appears to have made as much as could 

 be made out of the bare laws of association, unextended to the rest of 



1 " Observations," p. 74. 2 Youmans, "Xew Chemistry," p. 55. 



' " Observations," p. 75. 



