ON THE FORMATION OF CRYSTALLINE ROCKS. 253 



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

 in schistose rocks may serve for instruction in a philosophical point 

 of view. We see how easy it is, especiall}- in geology, for the ablest 

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

 facts. Moreover, even after the influence of mechanical pressure had 

 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 Brongniart,* d'Omalius, deBonnard,t Four- 

 net,! de Boblaye,§ Virlet,S A. Burat, de Boucheporn,^ Gras,** 

 Charles Deville, Coquand,tt Puton,:j;| Gueymard, Lor}', Angelot, 

 Drouot, Delanoue. 



■'' Sur les ophiolites ; siir Ics caractferes zoologiques dee formations. — {Annales des Mines 

 1821.) Sur le Cotentin — [Journal des Mines; 18J5.) 



f Annates des Mines, 1st series, vol. viii ; 1824. 

 Besides the memoirs, in wbiclr Fournet has published since 1836 very many pre- 

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

 learned profe.ssor has collected at the Faculty of Sciences of Lyons an interestifjg collection 

 ■which has been studied by many savants I shall again cite his Eludes sur les Alpes, (1845 

 to 1849.) 



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

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

 the question of metamorphism.- (Comjptes Rendus de I' Academie, 1838. Bidletin de la SocieU 

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



II Virlet long since made known numerous effects of metamorphism in Greece, and 

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

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

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

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



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

 has admitted that, by heating, the elementary matter of granite had given off iiuorites of 

 silicium and of the alcaline metal, which are the cause of the tiansformation of the neigh- 

 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 Savoy, and considered the spilitcs of this chain as metamorphic. 



ffCoquand has furnished very interesting facts, particularly \A describing the solfe- 

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



XX The work of Putqn on the metamorphi.sms which have occurred in certain rocks 

 of the Vosg'Js (1838) contains many well observed facts. 



