276 HISTORY OF MINERALOGY. 



though we are unable to follow either of them to 

 this point of union, we may learn from both in 

 what direction we are to look for it. If we regard 

 the best of the pure systems hitherto devised as in- 

 dications of the nature of that system, perfect both as 

 a chemical and as a natural-history system, to which 

 a more complete condition of mineralogical know- 

 ledge may lead us, we may obtain, even at present, 

 a tolerably good approximation to a complete clas- 

 sification ; and such a one, if we recollect that it 

 must be imperfect, and is to be held as provisional 

 only, may be of no small value and use to us. 



The best of the mixed systems produced by this 

 compromise again comes from Freiberg, and was 

 published by Professor Naumann in 1828. Most of 

 his orders have both a chemical character and great 

 external resemblances. Thus his Haloides, divided 

 into Unmetallic and Metallic, and these again into 

 Hydrous and Anhydrous, give good natural groups. 

 The most difficult minerals to arrange in all systems 

 are the siliceous ones. These M. Nauinann calls 

 Silicides, and subdivides them into Metallic, Unme- 

 tallic, and Amphoteric or mixed; and again, into 

 Hydrous and Anhydrous. Such a system is at least 

 a good basis for future researches; and this is, as we 

 have said, all that we can at present hope for. And 

 when we recollect that the natural-history principle 

 of classification has begun, as we have already seen, 

 to make its appearance in our treatises of chemis- 

 try, we cannot doubt that some progress is making 



