248 EXPEEIMENTS ON METAMORPHISM AND 



ogous to cementation. Other considerations which tended to the 

 conclusion that water had probably served as a vehicle of the heat 

 are due to Fuchs, Silliman and Dana,* and to Schalfautl.f Nor 

 must we fail to speak of the labors of Bischof, who, possessing great 

 critical judgment and knowledge of the resources of chemistry, did 

 not cease, during man}^ years, to combat the ultraplutonic ideas which 

 were in vogue at the time of which we are speaking. | Volger also, 

 following this example, has brought numerous arguments to bear 

 against the action of heat, which he even entirely rejects. 



After having studied the volcanic phenomena of Iceland in all 

 their principal peculiarities, Bunsen called attention to the action 

 of gas and water at temperatures comparable to those of the existing 

 fumaroles, and considered them as a cause of metamorphism at least 

 as powerful as heat.§ Cotta likewise, in describing the great ex- 

 amples of metamorphism in the Alps, remarks, with justice, that 

 such effects cannot have been produced without the cooperation of 

 water, which proceeded either from the humidity of the rocks or from 

 hot springs. II Still later, Delesse has examined, by help of the 

 chemical analysis, the nature of eruptive rocks and of those which 

 surround them at their point of contact.! Judging from a great 

 number of facts, he has also come to the conclusion that trap and 

 granitic rocks appear to have modified the rocks which surround 

 them, less by their own heat than by aqueous emanations which were 

 charged Avith different saline or acid substances.** 



At the same time that the observations of which we have just 

 spoken tended to cause the action of water in metamorphism to be 

 admitted, it was recognized, on the other hand, that granite, the erup- 

 tive rock to which the most energetic power of transformation over 

 the surrounding masses had been attributed, could not itself have 



^' If a rock is calcined 12 yards in depth, it must have been melted not less than half 

 this distance, where heat has been the cause of the transformation. The heat appears to 

 have had water for a vehicle. — [Silliman s Journal, vol. xlv, 1843.) 



f Die nemden geologischen Hypothesen unci ihr Verlialtniss zur Naiunoissenschaft iiberhaupl. 

 Leonard's Jarbuch, p. 858, 1845. 



% A work very rich in observation by M. Bischof was published from 1847 to 1855, 

 entitled, Lehrbuch der chemischen iind physikalischen Geologie. 



One of the principal arguments which Mr. Bischof develops against the dry way, con- 

 sists in the production of minerals resembling those of the crystalline rocks as pseudomorphg 

 or epiginies, that is to say, in conditions where the minerals cc>uld not have been formed 

 but in the wet way. He does not, however, attribute an important part to the vapor of 

 water, after remarking its feeble action on rocks both in the burning mine of Dutweiler, 

 which has been on fire for two centuries, and in the soffionis of Tuscany. 



§ Ueber den innern zusammenhang du pseudovulkanischen Erscheinungen Islands. 

 Annalen du Chirnie und Pharmade, vol. Ixii., p. 1, 1847. Ueber die Processe der Vulkanis- 

 chen Gesteinbildungen Islands. Poqg. Ann., pp. 83, 197, 1851 ; Leonhard's Jarb., p. 537, 

 1851. 



II Geologische Briefe aus den Alpen, p. 243, 1850. 



•[f Etudes sur le metamorphism. — {Annates des Mines, 5th series, vols, xii and xiii, 1857 

 and 1858.) 



«* It is a fact analogous to that which proves the association of metalliferous deposits 

 with eruptive rocks. 



