320 ANNUAL OF SCIENTIFIC DISCOVERY. 



furnaces of the Lauten valley, Hartz, in regular octahedrons and 

 dodecahedrons; also in lamellar and radiated concretions. Lead- 

 glance, he informs us, is often formed by sublimations in the chimneys 

 of furnaces, and the crystals are cubical with the usual cleavage ; and 

 crystals of magnetic iron sometimes incrust cavities in the stone or 

 brick-work of the furnaces. 



EXPERIMENTS UPON THE FORMATION OF MINERALS IN THE 

 HUMID WAY IN METALLIFEROUS REPOSITORIES. 



The following communication has been read before the French 

 Academy, by M. de Sanarmont. 



Geology has means of investigation which are peculiar to itself, and 

 now comprehend a certain number of special truths definitely acquired 

 to science. It is thus that geoleogy has been able, without foreign 

 aid, to characterize the manner of the formation of the sedimentary 

 rocks, and to arrange them in series ; it is thus that it has succeeded 

 in distinguishing in crystalline rocks, and in metalliferous repositories 

 different classes of which it can assign the probable origin ; and in so 

 far as it has not drawn conclusions too far removed from its fundamen- 

 tal principles, its anticipations have been almost always confirmed by 

 experiment. It is to mineralogical chemistry that geology owes the 

 useful experimental control of its rational conceptions. Crystalline 

 minerals have, in fact, a complete chemical origin; and a more 

 thorough study and knowledge of them must be advanced by chemical 

 experiment. 



Chemistry, then, can do much for geology by lending its means for 

 experiment ; but upon the condition of itself remaining purely geo- 

 logical, and of borrowing in its turn particular means of study, and 

 the general data which the science a priori, has collected upon all 

 the conditional peculiarities of structure, relative position, association, 

 or mutual exclusion, to which certain mineral species must needs 

 be subject. In a word, it is necessary that all the circumstances 

 where the natural operation has left characteristic traces, discovered 

 by the geologist, should reappear in the artificial operation of the 

 chemist. 



The experiments, then, of mineralogical synthesis should embrace 

 the different groups of mineral species which are united in nature, and 

 should support themselves upon certain probable geological inductions 

 concerning the formation of the beds which they inclose. Certain 

 isolated species have already bi'.en obtained, and principally those 

 which approximate to the usual products according to the dry method. 

 I have attempted to do more, and to discover some indices of the gen- 

 eral causes which have originated the different classes of metalliferous 

 beds. I commence this problem by the study of the concretionary 

 veins which approach most nearly to the existing formations, and the 

 principles I have just explained have been the starting point of the 

 researches I am about to submit to the Academy. 



The concretionary repositories seemed to be formed by solution ; 



