CHEMICAL AFFINITY. 167 



That there must be something in the constitution of mat- 

 ter, 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 hy- 

 pothetic 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 accept as an argument in favour of an 

 atomic theory, those combinations which are made to support 

 it by the application of an arbitrary notation. 



A similar straining of theory seems gradually obtaining 

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

 ery of cyanogen by Gay-Lussac was probably the first in- 

 ducement to the doctrine of compound radicals ; a doctrine 

 which is now generally, perhaps too generally, received in 

 organic chemistry. As, in the case of cyanogen, a body ob- 

 viously compound discharged in almost all its reactions the 

 functions of an element, so in many other cases it was found 

 that compound bodies in which a great number of elements 

 existed, might be regarded as binary combinations, by con- 

 sidering certain groups of these elements as a compound rad- 

 ical ; that is, as a simple body when treated of in relation to 

 the other complex substances of which it forms part, and 

 only as non-elementary when referred to its internal consti- 

 tution. 



