i5o CORRELATION OF PHYSICAL FORCES. 



in the character of the compound, and the same may be 

 predicated to some extent of an acid and an alkali ; but even 

 where the steps are sudden, and compounds only exist with 

 definite proportions, they cannot, in a multitude of cases, be 

 reconciled with the true idea of an atomic combination, i.e. 

 one to one, one to two, one to three, &c. 



Although, therefore, there are facts which show that there 

 is some restrictive law of combination which in numerous cases 

 limits the ratios in which substances will combine, nay, further, 

 which show many instances of a proportion between the com- 

 bining weights of one compound and those of another; although 

 there is also a remarkable simplicity in the combining volumes 

 of numerous gases, there remain very many cases to which 

 the doctrine of atomic combinations cannot fairly be applied. 



That there must be something in the constitution of 

 matter, or in the forces which act on it, to account for the per 

 saltum manner in which chemical combinations take place, is 

 inevitable ; but the idea of atoms does not seem satisfactorily 

 to account for it. 



By selecting a separate multiplier or divisor, chemists may 

 denote every combination in terms derived from the atomic 

 theory ; but they have passed from the original law, which 

 contemplated only definite multiples, and the very hypothetic 

 expressions of atoms, which the apparently simple relations of 

 combining weights first led them to adopt, they are obliged to 

 vary and to contradict in terms, by dividing that which their 

 hypothesis and the expression of it assumed to be indivisible. 



While, therefore, I fully recognise a great natural truth in 

 the definite ratios presented by a vast number of chemical 

 combinations, and in the per saltum steps in which nearly all 

 take place, I cannot join in evading the argument against the 

 atomic theory presented by those combinations which are 

 made to support it only by the application of an arbitrary 

 notation. 



A similar straining of theory seems gradually obtaining 

 in regard to the doctrine of compound radicals. The dis- 

 covery of cyanogen by Gay-Lussac was probably the first 

 inducement to the doctrine of compound radicals : a doctrine 

 which is now generally, perhaps too generally, received in 



