ON THE FORMATION OF CRYSTALLINE ROCKS. 253 



The history of the succession of ideas on the formation of lamellae 

 in schistose rocks may serve for instruction in a philosophical point 

 of view. We see how easy it is, especially in geology, for the ablest 

 minds to err when they deviate from the path of observation and ot 

 facts. Moreover, even after the influence of mechanical pressure ]^ad 

 suggested the probable cause of the phenomenon, it was ten years be- 

 fore one of the most simple experiments which it would seem ought 

 to have been immediately thought of, was brought forward to verify 

 this induction. 



CHAPTER VII. 

 NOTICE OF OTHER OBSERVERS WHO HAVE INVESTIGATED METAMORPHISM. 



The facts upon which the doctrine of metamorphism is based have 

 been observed in all regions of the globe, especially during the thirty 

 years that attention has been called to the subject by many other ge- 

 ologists, some of whom have very much exaggerated or falsified the 

 bearing of the phenomenon. The observers are so numerous that it 

 would be impossible, without lengthening this work beyond measure, 

 to do more than notice the principal names. They are : 



In France — Alexander Brongmart,*d'Omalius, deBonnard,t Four- 

 net,:}: de Boblaye,§ Virlet,i A. Burat, de Boucheporn,1[ Gras,*^ 

 Charles Deville, Coquand,tt Puton,|| Gueymard, Lory, Angelot, 

 Drouot, Delanoue. 



•"■ Sur les ophiolites ; sur les oaractferes zoologiques deg formations. — (Annales den Mines 

 1821.) Sur le Cotentin — {Journal des Minei ; 18J5.) 



f Annales des 3Itnes, Ifit geries, vol. viii ; 1824. 



; Besides the memoirs, in which Foiiruet has published since 1836 very many pre- 

 cise observations and ingenious suggestions on metamorpliism, as I have said above, this 

 learned professor iias collected at the Faculty of Sciences of Lyons an interesting collection 

 which lias been studied by many savants I shall again cite his Etudes sur les Alpes, (1845 

 to 1849.) 



§The discovery in the formations of transition of schists, containing at the same time 

 made and niany fossils, by Boblaye, has introduced a new element really positive into 

 the question of metamorphism.- (Cbmptes Rendus de l' Academic, 1838. Bidhtin dc la Sodete 

 Geologique, 1st series, vol. x, p. 227. ) 



P Virlet long since made known numerous effects of metamorphism in Greece, ami 

 has even extended the ideas on metamorpliism to the utmost in applying them to eruptive 

 rocks, such as granite, protogerie, trachite. — {Geologie de la Grece, pp. 67, 184, 294, 298, 304, 

 and 306. Bulletin de la SociM Geologique de France, vol. vi, pp. 279 and 313, 1834 ; vol. vii, p. 

 310, 1835 ; 1st series, vol. xiv, p. 501. ) 



^ De Boucheporn, in exaggerating the action which I had previously attributed to fluor, 

 has admitted that, by lieating, the elementary matter of granite had given off fluorites of 

 silicium and of the alcaline metal, wliich are tlie cause of the transformation of the neigli- 

 boring rock, (page 271 of his work.) His original idea on the action of cyanogen in the 

 formation of the globe merits attention. 



"~" Gras has made important observations on the crystalline rocks of the Alps, 

 Dauphin and vSavoy, and considered the spilites of this chain as metamorphic. 



ffCoquand has furnislied very interesting facts, particularly in describing the solfa- 

 taires of Tuscany, and in studying the formation of gypsum and of dolomite. 



JJThe work of Futon on the metamorphisms which have occurred in certain rocks 

 ©f the Vosgos (1838) contains many well observed facts. 



