ON MINERAL VEINS. 403 



to those; in which case the catalogue might be still 

 further increased. 



The earthy minerals which may be modified by 

 artificial fire, or which undergo the action of heat 

 without destruction, are the carbonats of lime, barytes, 

 and strontian, and the phosphat of lime. Silica is 

 sublimed in a crystalline form, as I have proved. Of 

 the metallic minerals, every metal may be sublimed 

 by artificial heat; and they all admit of being cry- 

 stallized by fusion. All the sulphurets can be fused; 

 all appear capable of being sublimed; and, probably, 

 the whole can also be produced in this way, by a 

 direct combination of their ingredients. All the 

 oxydes are produced from the metals by heat, and 

 some of them admit of being volatilized. Under these 

 circumstances also, some of them crystallize ; as is the 

 case with the red oxyde of copper formed in the ca- 

 vities of metallic vessels in Pompeii. It is probable 

 that some of the metallic salts, the arseniats for ex- 

 ample, can be produced in this way; but I cannot 

 quote any satisfactory experiments on a subject which, 

 in all its bearings, is well worthy the attention of those 

 chemists who are interested in geology, and whose 

 leisure is greater than my own. 



In examining the evidence which nature affords on 

 this question, the following is a list of such earthy 

 minerals as are found in the situations above men- 

 tioned. It is probable that many are omitted; as no 

 evidence but what seemed unexceptionable has been 

 taken; and, in examining the entire catalogue of 

 minerals, it will easily be found that there are some 

 of which the origin still remains uncertain, and which 

 are therefore excluded both from the aqueous and 

 the igneous lists. 



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