238 EXPERIMENTS ON METAMORPHISM AND 



the name of metamorphism, the changes which, according to the 

 theory of Hutton, the rocks of sedimentary origin have undergone 

 by the action of central heat: this is the name that since then has 

 been adopted.* 



But, at this epoch, what excited attention in the highest degree 

 was the work of Leopold de Buch, on the geology of the southern 

 Tyrol, published in 1822,t Already in the last century, as we have 

 before said, Arduino had attributed the origin of the dolomite of 

 Vicentine to a transformation of limestone. Twenty years after, 

 Heim, a German geologist, whose works contain a great number of 

 facts which were then new and judiciously observed, made observa- 

 tions in Thuringia which led him to the same conclusion.:]: 



Leopold de Buch presented this hypothesis anew in a striking 

 manner, while giving it a wider scope. For him the colossal and 

 ruptured masses of dolomite in the valley of Fassa are only limestones, 

 into whose innumerable fissures the eruptions of melaphyre, which 

 raised and broke them up, have introduced magnesia in a state of 

 vapor. He was thus brought to the conclusion that it is not heat 

 alone, but also chemical emanations which have had an influence 

 in the transformation of rocks. || This was, moreover, increasing the 

 importance of mechanical dislocations by showing how they might 

 open sources of sublimations or vapors, which afterwards act upon 

 the rocks. It was, in a word, a new point of view introduced into 

 the science by one who was then already at the head of geologists. 



Later research has shown that certain modifications must be applied 

 to this conclusion; but the questions which the bold hypothesis of 

 the metamorphism of dolomite gave rise to elicited investigations 

 which have enriched science. An idea which leads to discoveries 

 rests, in general, on some profound relation and denotes an inventive 

 mind. 



The Alps, which w^ill ever be a classic region for geology, as much 

 on account of the energies which produced this chain as of the deep 

 and imposing rents through which it exposes its internal construction, 

 have furnished, together with Scotland, the fundamental observations 

 for the theory of metamorphism. 



Previously, in a memoir which marks an epoch in science, and 

 which appeared at the time that Cuvier and Brongniart published 



*Metamorphic rocks form a part of his hypoyene rocks. 



fLettres sur la Geologie de Tyrol meridional — {Annales deChimie tt de Physique, vol. xiii^ 

 1822. Taschenbuch, vol. xix and xx, 1824.) 



JSpeaking of the cavernous dolomites of the Zechstein, he says that the same kind of 

 dolomite is found in the Muschelkalk ; that it is only a peculiarity of limestone. It wa& 

 not known at this time that this rock contained magnesia. This modification of limestone, 

 he adds, is in relation with the accidents which have been produced from below upwards, 

 and, among natural forces, vapors are the only ones which could have produced such an 

 action ; they have at the same time formed gypsum, which is always associated with the 

 dolomite. — Heim, Geologische Beschreibung des Ihuringerwaldgehirgs, 1806. 



||However, before this time Breislach, in his excellent description of the Solfatara of 

 Puzzuoli, had shown that vapors alter rocks. Cordier, iu 1820, had also shown that 

 alunite results in general from the action of sulphurous vapors on feldspathic rocks. — (Annale& 

 des Mines, 1st series, vol. v, p. 303 ) 



