126 ON SYSTEMATIC ZOOLOGY. 
where the other begins. We make use of an artificial 
system to become acquainted with the name of a species ; 
and to learn all that has been written upon its peculiar 
structure. We turn to the natural system, to know the 
probable station of this species in the scale of being, 
the affinities it possesses to others, and the analogies 
by which it is related and represented. Hence the per- 
fection of an artificial system, as we have frequently in- 
timated, consists in the clearness and precision of its 
subdivisions, and the facilities which it affords to de- 
termine the name of the object we are in search of. | In 
this respect, a good artificial system is to be judged by 
the same rules as those by which we should decide on 
the merits of a copious index to a voluminous publica- 
tion, tor the purposes of both are the same: both are 
equally useful, and the merit of both lies in clearly 
directing the reader to the precise point upon which he 
desires information. A good artificial system is, there- 
fore, not only a useful, but even, in some respects, a 
valuable, invention, requiringS much more skill than is 
generally supposed; and it is, perhaps, much more 
adapted for general use than any other. The most 
admirable classification of this sort ever invented, is that 
denominated the Sexual System of Plants, by Linneus. 
Many natural assemblages are preserved, without any 
great violation of the principles on which he set out. 
This is always a great recommendation to an arti- 
ficial system, yet it is by no means necessary to its 
formation. Natural affinities may be overlooked, wher- 
ever they interfere with precision of arrangement: 
the first are secondary, the latter primary. We open 
an artificial system to come to the knowledge of a mat- 
ter of fact ; but if we wish to proceed farther, and to 
know how this fact bears upon other facts, we turn to 
the natural system. Such are the uses of the two methods 
of classification upon which we have been speaking, and 
such the theoretic distinctions by which they are sepa- 
rated. Between them, however, is a third sort of 
system, which, from combining artificial division with 
