INDUCTION. 



we are affirming something to be uniformly coexistent with 

 the properties by which the kind is recognised ; and that is 

 the sole meaning of the assertion. 



Among the uniformities of coexistence which exist in nature, 

 may hence be numbered all the properties of Kinds. The 

 whole of these, however, are not independent of causation, 

 but only a portion of them. Some are ultimate properties, 

 others derivative ; of some, no cause can be assigned, but 

 others are manifestly dependent on causes. Thus, pure atmo- 

 spheric air is a Kind, and one of its most unequivocal pro- 

 perties is its gaseous form : this property, however, has for 

 its cause the presence of a certain quantity of latent heat ; 

 and if that heat could be taken away (as has been done 

 from so many gases in Faraday's experiments), the gaseous 

 form would doubtless disappear, together with numerous 

 other properties which depend on, or are caused by, that 

 property. 



In regard to all substances which are chemical compounds, 

 and which therefore may be regarded as products of the juxta- 

 position of substances different in Kind from themselves, there 

 is considerable reason to presume that the specific properties of 

 the compound are consequent, as effects, on some of the pro- 

 perties of the elements, though little progress has yet been 

 made in tracing any invariable relation between the latter and 

 the former. Still more strongly will a similar presumption 

 exist, when the object itself, as in the case of organized beings, 

 is no primeval agent, but an effect, which depends on a cause 

 or causes for its very existence. The Kinds therefore which 

 are called in chemistry simple substances, or elementary natural 

 agents, are the only ones, any of whose properties can with 



singly, being a joint property of that and of other Kinds. The colour and 

 brightness of the diamond are common to it with the paste from which false 

 diamonds are made ; its octohedral form is common to it with alum, and 

 magnetic iron ore ; but the colour and brightness and the form together, iden- 

 tify its Kind ; that is, are a mark to us that it is combustible ; that when 

 burnt it produces carbonic acid ; that it cannot be cut with any known sub- 

 stance; together with many other ascertained properties, and the fact that 

 there exist an indefinite number still unascertained. 



