1S2 Prof. Mitscherlich on (lie Production of 



The primitive mountains are distinguished from the vol- 

 canic productions, chiefly in their containing lime and mag- 

 nesia in the state of carbonates, while they form silicates and 

 bisilicates with the silica in volcanic rocks. It is conceivable, 

 that the silica, which in a higher degree of temperature at the 

 ordinary pressure of the atmosphere, drives away the carbo- 

 nic acid, is on the other hand expelled hy the carhonic acid 

 under the influence of a high pressure. It is not therefore 

 surprising to find quartz crystals in Carrara marble. But, as 

 at the period of the formation of volcanic rocks, this high 

 pressure, produced by the evaporation of the water of the 

 sea, did not take place any longer, we find in them the same 

 combinations which we obtain in our laboratories, and in me- 

 tallurgical processes. 



It is proved by many observations, that the level of the sea 

 must have been, at some ancient period, higher than it is at 

 present. This can be easily accounted for, if we consider that 

 water heated must be more expanded than the solid earth. If 

 we suppose with M. de la Place, that the average depth of 

 the sea is 96,000 feet, and assume the dilatation of the earth to 

 be equal to that of glass, we find, that at a temperature of 100° 

 centigr., the sea would be 4000 feet higher than it is at pre- 

 sent, and that it would cover most of the secondary moun- 

 tains. The melted masses shrink during their cooling. If 

 this happens in large masses, cavities, garnished with crystals, 

 must result, geodes, &c. 



Iiiferences d?-azvn in regard to metallurgical processes. — The 

 process of the melting of copper ore at Fahlun may be ex- 

 plained as follows, viz. The ore consists of copper-pyrites, 

 and iron-pyrites, of two varieties ; one of them is rich, and the 

 other very much mixed with quartz. They are first roasted, 

 and thereby converted into a mixture of sulphuret, oxide, and 

 sulphate. The roasted mineral is now melted in the propor- 

 tion of three parts of the rich ore to one part of the quarlzy 

 variety. But the melters must be always attentive to the fur- 

 nace, and add now part of the one, now part of the other of' 

 the two kinds of ore, so as always to have the slags, consisting 

 of a bisilicate of protoxide of iron . This slag is lamellar, and 

 crystallizes like pyroxene. At the same time metallic com- 

 pounds arc obtained, consisting of sulphuret of iron, and sul- 



