$8 M. Virlet on the Transformation of Rocks. 



veins ? Numerous other facts, although not yet fully explained, 

 have been brought forward and admitted without dispute. For 

 example, I have proved that the emery of Naxos comes from 

 veins, and consequently had been formed, like the greater num- 

 ber of specular iron ores, by means of volatilization and sublima- 

 tion ; yet the corundum and oxide of iron, the mixture of which 

 constitutes emery, are not more volatile than the carbonate of 

 magnesia, which forms the subject of dispute. 



Since our chemical knowledge, then, does not always enable 

 us to explain the phenomena whose existence we can prove, does 

 it follow that we ought to call them in question ? Has nature 

 no mode of acting which surpasses our knowledge ? And could 

 she not proceed, for instance, by means of double chemical de- 

 composition ? On this supposition, the phenomenon will admit 

 of easy explanation. It is well known that all the muriates are 

 volatile, or at least susceptible of sublimation. Magnesia might 

 then easily reach the state of a muriate, and occasion the for- 

 mation of a soluble hydrochlorate of lime, which would be car- 

 ried off by the infiltration of water ; while the magnesia, on the 

 contrary, would be combined with that portion of the carbonic 

 acid set at liberty, and would thus serve to form the double car- 

 bonate of magnesia and of lime, which constitutes dolomite, pro- 

 perly so called. In this there is certainly nothing inadmissible 

 or contrary to reason, inasmuch as the hydrochloric acid gas is 

 one of the gases most frequently disengaged from volcanos, and 

 the muriates ought to have been disengaged more abundantly 

 in former times, if we admit, with geologists of the modern 

 school, that the immense deposits of rock-salt which exist in 

 saliferous formations, are deposited by volatilization, in the midst 

 of the strata which they penetrate. 



I am, therefore, of opinion that the modifications of rocks of 

 the second class may henceforth be all explained by means of 

 double decomposition — a process which has enabled one of my 

 friends, M. Aime, to produce in the laboratory crystallized specular 

 iron ore, analogous to that of the Island of Elba, as well as pure 

 iron equally well crystallized — a substance hitherto unknown to 

 mineralogists ; whence I conclude that the time is not perhaps 

 far distant when we shall be able to produce with ease all the 

 species of precious stones, without even excepting the diamond. 



