260 EXPERIMENTS ON METAMORPHISM AND 



which have thrown much light on very important phenomena.* 

 Operating with the aid of water at a temperature of 130° to 300° 

 centigrade, he succeeded in producing, in a crystallized state, the 

 principal minerals which characterize metallic veins — among others, 

 quartz, t spathic iron, the carbonates of manganese and zinc, sulphate 

 of baryta, sulphide of antimony, mispickel, and red silver. To com- 

 prehend at this time all the importance of the problem which was 

 thus solved by this savant, we must remember that until then we 

 had not been able to imitate the greater part of the minerals occuring^ 

 in veins. Now, the most characteristic species of these formations, 

 numbering more than thirty, have been reproduced by a process 

 similar to that which observation led us to suppose, and by the aid 

 of the element the most widely distributed in hot springs. This 

 memorable achievement, for the first time, shoAved in geology that 

 an induction relative to an entire order of facts may be demonstrated 

 by experimental synthesis. 



De Senarmont has also shown that the sole action of water suf- 

 ffices, with the aid of a high temperature, to isolate the bases of cer- 

 tain salts. It is thus that anhydrous oxide of iron and crystallized 

 alumina or corundum have been produced by the decomposition of 

 solutions of chloride of iron and chloride of aluminium. Brochantite 

 (sub-sulphate of copper) and azurite have been recently obtained by 

 the same process. Up to that time the humid way had not served 

 to produce anhydrous silicates. I have been able to do this by a 

 series of experiments, the principal results of which I shall give in 

 the third part.:}; 



We may add that nature herself continues to make daily experi- 

 ments (if the expression may be used) of the same kind with those 

 which we only perform with so much difficulty, employing probably 

 processes analogous to those which she has resorted to from the most 

 remote ages. Unfortunately these reactions take place in regions 

 that we can very rarely reach. It is only in a very few instances 

 that we can be witnesses of the formation of contemporaneous 

 minerals. It is sufficient to go down a few j-ards into the subsoil of 

 Plombieres, and to enter the masses infiltrated for centuries by 

 thermal waters to discover sulphuret of copper in crystals identical 

 with those of Cornwall, and a whole series of zeolites, arranged as in 

 basaltic rocks. § What would be the result if we could penetrate 

 deeper into the ducts through which these hot springs ascend? 



~ Experiences sur la formation artificielle par vole humide de quelques espfeces min^rales- 

 qui ont pu se former dans les sources thermales sous 1 'action combiu^e de la clialeur et de 

 la pression. — {Annales de Chimie et de Physique, vol. xxviii, p. 693, 1849.) Experiences sur 

 la formation des mineraux par voie humide dans les gites metallif^res concretionnes. — 

 {Annales de Chimie et la Physique, vol. xxxii, 1851.) 



f Anzeigtn, p 557, 1845. 



j Observations sur le ni6tamorphisme et recherchcs experimentales sur quelques-uns de& 

 agents qui ont pu le produire. — [Annales des Mines, 5th series, vol. xii, p. 289, 1857 ; 

 Bulletin de la Sociitie GMogique de France, 2d series, vol. xv, p. 97.) 



§ Memoire sur la relation des sources thermales de Plombieres avec les filons mfetallif6res 

 et sur la formation contemporaine des zeolites. — {Annales des ilines, 5th series, vol. xiii, p. 

 227.) The formation of iron pyrites, which is a mineral so widely dispersed, has been but 

 very seldom seen ; and first by Longchampat Chaudesaigues. Bischof met with it at Brohl, 

 and Bunsen in Iceland. / 



