CLASSIFICATION. 435 



the classification which would involve the least peril of similar rap- 

 prochcmcns, we should return to the obsolete division into trees, shrubs, 

 and herbs, which although of jn-imary importance with regard to mere 

 general aspect, yet (compared even with so petty and unobvious a dis- 

 tinction as that into dicotyledones and monocotyledones) answers to so 

 few ditterenccs in the other properties of ])lants, that a classification 

 founded on it (independently of the indistinctness of the lines of 

 demarkation,) would be as completely artificial and technical as the 

 Linneean. 



Our natural groups, therefore, must often be founded not upon the 

 obvious, but upon the unobvious properties of things, when these are of 

 gi-eater importance. ,But in such cases it is essential that there should 

 be some other property or set of properties, more readily recognizable 

 by the observer, which coexist with, and may be received as marks of, 

 the properties which are the real groundwork of tlic classification. A 

 natural aiTangement, for example, of animals, must be founded in the 

 main upon their internal structure, but (as M. Comte justly remarks) it 

 would be absurd that we should not be able to determine the genus and 

 species of an animal uithout first killing it. On this ground, M. Comte 

 gives the preference, among zoological classifications, to that of INI. de 

 ElainWlle, founded upon the differences in the external integuments ; 

 differences which conespond, much more accurately than might be sup- 

 posed, to the really important varieties, both in the other parts of the 

 structure, and in the habits and history of the animals. 



This shows, more strongly than ever, how extensive a knowledge of 

 the properties of objects is necessary for making a good classification 

 of them. And as it is one of the uses of such a classification that by 

 drawing attention to the properties on which it is foiinded, and which 

 if the classification be good are marks of many others, it facilitates the 

 discovery of those others ; we see in what manner our knowledge of 

 things, and our classification of them, tend mutually and indefinitely to 

 the improvement of one another. 



We said just now that the classification of objects should follow 

 those of their propeities which indicate not oidy the most numerous-, 

 but also the most important peculiarities. \Vliat is here meant by 

 importance ? It has reference to the particular end in view: and the 

 same objects, therefore, may admit with })ro]iriety of several different 

 classifications. Each science or art fi)rins its classification of things 

 according to the properties which fall within its special cognizance, or 

 of which it must take account in order to accomplish its peculiar prac- 

 tical ends. A fanner does not divide plants, like a botanist, into 

 dicotyledonous and monocotyledonoiLS, but into useful plants and weeds. 

 A geologist divides fossils, not, like a zoologist, into families correspon- 

 ding to tliose of living species, but into fossil^ of the secondary and of 

 the tertiary periods, above the coal and below the coal, &c. Wliales 

 are or are not fish, according to the purpose for which we are consider- 

 ing them. " If we are" speaking of the internal structure and physiology 

 of the animal, we must not call them fish ; for in these respects they 

 deviate widely from fishes ; tliey have warm hlood, and produce and 

 suckle their young as land quadrupeds do. l^ut this would ncjt prevent 

 our speaking of the whale fishery, and calling such animals Jish on all 

 occasions connected with this employment; fJir the relations thus arising 

 depend upon the animal's living in the water, and being caught in a 



