336 HISTORY OF MINERALOGY. 



seems to have had some success in given a common type to then 

 chemical formulae, as there is a common type in their crystallization. 



[2nd Ed.] [It will be seen by the above account that Prof. Mitsch- 

 erlich's merit in the great discovery of Isomorphism is not at all nar- 

 rowed by the previous conjectures of M. Fuchs. I am informed, more- 

 over, that M. Fuchs afterwards (in Schweigger's Journal] retracted the 

 opinions he had put forward on this subject.] 



Dimorphism. My business is, to point out the connected truths 

 which have been obtained by philosophers, rather than insulated dif- 

 ficulties which still stand out to perplex them. I need not, therefore, 

 dwell on the curious cases of dimorphism ; cases in which the same 

 definite chemical compound of the same elements appears to have two 

 different forms ; thus the carbonate of lime has two forms, calcspar 

 and arragonite, which belong to different systems of crystallization. 

 Snch facts may puzzle us ; but they hardly interfere with any received 

 general truths, because we have as yet no truths of very high order 

 respecting the connexion of chemical constitution and crystalline form 

 Dimorphism does not interfere with isomorphism ; the two classes of 

 facts stand at the same stage of inductive generalization, and we wait 

 for some higher truth which shall include both, and rise above them. 



[2nd Ed.] [For additions to our knowledge of the Dimorphism of 

 Bodies, see Professor Johnstone's valuable Report on that subject in the 

 Reports of the British Association for 1837. Substances have also 

 been found which are trimorphous. We owe to Professor Mitscherlich 

 the discovery of dimorphism, as well as of isomorphism : and to him 

 also we owe the greater part of the knowledge to which these disco- 

 veries have led.] 



CHAPTER VII. 



ATTEMPTS TO ESTABLISH THE FIXITY OF OTHER PHYSICAL PROPER- 

 TIES. WERNER 



THE reflections from which it appeared, (at the end of the last 

 Book,) that in order to obtain general knowledge respecting 

 bodies, we must give scientific fixity to our appreciation of their pro- 

 perties, applies to their other properties as well as to their crystalline 



