Reflections on some Miner aloglcal Systems, 293 



affinity in their chemical compositions, belong to the same 

 species. (June 1805 *.) 



* I shall not stop to give examples proving that the 3d 

 rule has been abused : it has been violated at almost every 

 step. In the greater part of the minerals which are but 

 varieties of the same species, if we examine them closely, 

 we shall find more than three specific characters which are 

 dissimilar. The division of characters into generic, specific, 

 and characters of variety, and the little precision which ex- 

 ists in all that has been said on the number and importance 

 of characters, render this examination irksome. 



As to the 4th Art. I asked the celebrated author of the sy- 

 stem of external characters, if there existed a sufficient dis- 

 parity between the properties of sulphated barytes and sul- 

 phated strontian to constitute them two species ; and he 

 answered No. Here chemistry makes two genera where 

 the external characters would not have two species. 



For the 5th Art. there is not less difference between the 

 garnet and pyrope, quartz and eisenkiesel [iron flint, Jame- 

 son], beryl and emerald, than between the common or 

 compact feldspar and hohhpath {made of the French), pot- 

 ter's clay and sckieferthon [slate clay of Jameson, and argile 

 feuilletee of Brogniart], mountain cork [asheste tresse of 

 Haiiy, or A. suberiforme of Brogniart], and amianth, cal- 

 careous spar, pisolite [peas lone of Jameson, and chaux car' 

 bonatee concreiionte of Haiiy] and compact, common and 

 fibrous limestone. 



I have chosen only a few examples ; but they are suffi- 

 cient to prove that there is not one of the rules proposed to 

 serve as a basis to the system which has not been in- 

 fringed ; sometimes one prevails, sometimes another; and 

 we can only refer the consequent instability to the insuffi- 

 ciency of the principles. 



PHILOSOPHERS AND PHILOSOPHY OF FREYBKRG. 



During a residence of 18 months at Freyberg, where I 

 had every day occasion to admire the precision and accuracy 

 with which the learned professor recognized minerals at the 

 first view, and where I was more than ever convinced by 

 the example of others of the difference which exists between 

 the institution of species and the knowledge of individuals, 



* Professor Jameson has even gone further, and divided, after Werner, 

 beryl into two subspecies, calling the one "Jirst subspecies, precious beryl" 

 (beryl of Kirwan), and the other (i srcoiid subspecies, schorlous beryl," the 

 pyenite of Haiiy, and shorlite of Kirwan ; thus indicating a relation in nu- 

 pierical order which has no existence in nature. — Than 3. 



T 3 I ncg- 



