1822.] Sixth Edition of his Sysleni of Chemstiy. '273 



the method published in the Edinburgh Journal ; but neither of 

 these accounts puts it in my power to understand the nature of 

 the arrangement. Mr. Jameson's last edition is a cypher with- 

 out a key. Under these circumstances, I thought myself obliged 

 to omit my references to Jameson's System. I could not 

 refer to the old edition after the author had pubHshed a new- 

 one ; and I could not refer to the new edition, because I did not 

 miderstand it. Thus circumstanced, I thought the best thing I 

 could do was to refer to Hoffman's Mineralogy, instead of 

 Jameson's. It contains the Wernerian descriptions in the very 

 words of Werner ; and is the original from which most of Jame- 

 son's descriptions are taken. ^ 



But even if I had understood Mohs's system, I question if 1 

 should have adopted it, because it is not adapted to a chemical 

 view of minerals. If Mohs succeed in establishing an artificial 

 system which will enable the student to find out the name of 

 any mineral of which he may happen to have a specimen, he will 

 perform a very useful task. But surely it will not be said that 

 the last edition of Jameson's Mineralogy is in this predicament. 



In a chemical treatise, the composition of minerals is the 

 most important point. Now Mohs has not paid any attention to 

 the composition of minerals, but has been guided by something 

 respecting the crystalline shape which he has not put it in our 

 power to understand. 1 shall give one order as an example, and 

 I select it the rather because all the minerals arranged in it 

 axe chemical compounds. 



Order VI. — Baryte. 



Genus I. — Lead Spar. 



Sp. 1. Sulphate of lead, 



2. Molybdate of lead, 



3. Chromate of lead, 



4. Phosphate of lead, 



5. Carbonate of lead. 



Genus II. — Hal-BoryL 



Sp. 1. Carbonate of barytes, 



2. Sulphate of barytes, 



3. Carbonate of strontian, 



4. Sulphate of strontian. 



Genus III. — Tungsten, 

 Sp. 1. Tungstate of lime. 



Genus IV. — Calamine^ 



Sp. 1. Sihcate of zinc, 



2. Anhydrous carbonate of zinc, 



3. Hydrous carbonate of zinc. 

 ^ew Series, vol, in. t 



