PREFACE. X 



principle now promulgated ; but, the necessity of 

 fixing the determination of species, on a certain and 

 permanent basis, outweighs every other consideration . 

 Indeed, the difficulty, that will attend the use of 

 the proposed rule, must chiefly arise from our im- 

 perfect knowledge of reliquia ; which, in certain in- 

 stances, prevents the reduction of detached parts 

 into individual species. This difficulty, however, 

 will grow less, as our knowledge of these subjects 

 increases ; and to meet the present state of the 

 study, I think it will be sufficient to adopt, for a 

 time, what I have denominated temporary species. 

 V. p. 194. &c. 



It will not here, perhaps, be foreign to the 

 subject, to remark, that in Botany and Zoology 

 what constitutes a species has long been fixed and 

 acknowledged ; while in Mineralogy, it seems unde- 

 cided if species even exist ! In the determination of 

 minerals, neither the integral molecule (i) assumed 

 by Haiiy and Dolomieu, nor the union of external 

 characters and internal composition, proposed by 

 Werner, for the construction of species, has been uni- 



() Doubtless, the nearest approximation towards the esta- 

 blishment of a natural principle, in the determination of the 

 mineralogical species, that has yet been made. 



b 



