, 222. THEORY OF T11E SYSTEM. 327 



mediately follow each other, or produce among themselves 

 a coherent fragment of the series. Thus, not only R, 

 R + 1, R -|- 2 ... but also R ... R + n ... (P + n) m ... 

 R + eo will answer the idea of what is meant by a transi- 

 tion. It is the same with the transitions in any other se- 

 ries, for instance, in the shades of colour, &c. ; though in 

 these it must be applied with the necessary degree of cir- 

 cumspection. In the forms of crystallisation, this like- 

 wise becomes necessary in respect to limiting forms, since 

 these are common to some of the series, in some cases even 

 to all the series of the same system of crystallisation. 



Transitions exist only within the species, as it evidently 

 follows from the preceding considerations ; hence there can 

 lc no transition from one species into another. 



Many examples of this kind of transitions may be found, 

 not in nature, but in several mineralogical books. Of 

 these it may be maintained, that wherever the transition is 

 correct, the determination of the species is erroneous, and 

 vice versa,) that the transition is falsely stated, if the de- 

 termination of the species be correct. 



From the continuity of the transitions, or of the series 

 of characters from which they depend, we may infer, that 

 there is a remarkable connexion within the natural-histori- 

 cal species, by which all the differences occurring in its in- 

 dividuals may be joined into a whole. Thus we become 

 capable of comprehending the variety of inorganic nature. 

 For the very same reason also, it is contrary to the real 

 interest of Mineralogy to divide or subdivide the species, 

 and to distinguish sub-species and kinds. The purpose of 

 such divisions is to facilitate the general survey of the 

 species ; but this indeed would rather be assisted by establish- 

 ing the connexion between its individuals, if this should 

 happen to be still wanting, than by such divisions, which 

 render it less evident. 



With those divisions into sub-species and kinds, which 

 have hitherto been in use, it has very often been the case, 

 that an individual was really found to belong to the species, 

 and yet to none of its sub-species. This has been the con- 



