228 



MINERALOGY. 



[Sect. VIII. 



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insoluble by our processes and infusible in our furnaces, 

 and some of them moreover belong to the class of gems. 

 M. Ebelmen inferred that^ inasmuch as many substances 

 in solution in water crystallize when the water is 

 evaporated, he would obtain certain minerals if he dis- 

 solved their elementary 



of igneous fusion) 



substances 



state 



in some body (in a 

 so doing, and which 

 at a still higher temperature would evaporate and leave 

 the elementary substances to adjust themselves in a crys- 

 talline form. Most perfect success attended the labours 

 founded on this view, and in this manner he obtained 

 crystals identical with rubies, spinels of various colours, 

 soberyl, chrysolite, and others. Crystals of emerald 

 were also formed from pounded emerald. The crystals 

 of clirysoberyl were of sufficient size to have their 

 optical properties tried, and were found identical with 

 those of the natural mineral. 



To classify the natural substances described under the 



Cli 



head of niioeralosfv, 



very various methods have been 



adopted, chiefly, however, divisible into those based 

 upon their external characters or chemical composition. 

 The following is that adopted by M. Dufrenoy in 1845, 

 founded on chemical comnosition. 



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