246 EXPERIMENTS ON METAMORPHISM AND 



I can only cite here the important investigations made for this pur- 

 pose by Fourier, Lagrange, Laplace, and Poisson.* 



In short, it has been by several very different paths that we have 

 come to admit the idea of a central heat as a fundamental idea in 

 geology, and to recognize the importance of the doctrine of metamor- 

 phism which attaches itself to it as an effect to its cause. 



C H A P TE R Y. 



MODIFICATIONS WHICH HAVE TAKEN PLACE SINCE THE TIME OF HDTTON IN 

 IDEAS RELATING TO METAMORPHISM. f 



Up to the time to which our third chapter brought us, that is to 

 say, during the first third of this century, heat aided by certain vola- 

 tile substances had been considered, after the example of Hutton, as 

 almost exclusively the cause of metamorphic phenomena. It was 

 thought that the transformed rocks had crystallized, after having 

 been softened and perhaps penetrated by the neighboring or subja- 

 cent igneous masses..! We shall see further on that all the synthetic 

 experiments of metallurgical works and of laboratories seemed com- 

 pletely to ratify this view of the subject. Certain more attentively 

 observed facts, however, arose to combat this generally admitted 

 hypothesis. It was in vain that, to do away with the serious objec- 

 tions which were raised, the action of cementation, of electricity, § and 

 of the possible solution of certain silicates, the one by the other, were 

 appealed to. Grave doubts had sprung up, and from that time they 

 only continued to increase. At this moment a new way seemed to 

 open; Ave shall presently see who were those that first entered 

 upon it. 



It was first ascertained that metallic veins could not, for the most 

 part, have been filled either by means of fusion or of sublimation, 

 but by matters held in solution in water which was at a high tempe- 

 rature. 



«Note sur le rapport qui existe entre les refroidissement progressif de la masse du globe 

 terrestre et celui de la surface. — (Compies Rendus, vol. xix, 1844, and l Imtitut, p. 32, 1845. 

 Memoirc sur la theorie mathematique des temperatures terrestres.— ^n«aZ«s des Chimk et de 

 Physique, vol. il, p. 387.) Several important memoirs by Mr. Hopkins and Mr. Hennessy. 

 t Instead of attributing, as did Hutton, the heat subsequently acting upon certain sedi- 

 ments to the temperature of the bottom of the sea, which we now know to be very low, 

 it is explained by other causes, as we shall see in the third part of this work. 



X Boue. m6moire cited above, 1824. — (.4wiate de Chimie et de Physique, 2d series, vol. Ix, 

 p. 291, 1835. — Soc>eti6 des Sciences de Lyon, 1 845. — Bulletin de la Societie Geoloyique de France, 2d 

 series, vol. ix, p. 222.) 



Fournet, who represented this school in France, compared these phenomena to the 

 absorption of the sides of a cupell. He tried to prove by experiment that argillaceous 

 schists submitted to the combined influences of heat and of certain fusible bodies, will be 

 penetrated by them with the greatest ease, and will thus undergo chemical action. The 

 quartz nodules (ganglions) found in micaschisjs were due to this cause. Quartz, in con- 

 sequence of a peculiar kind of sur/usion, might be consoliilated after more fusible substances. 

 It is thus that Fournet explains the alteration of the eruptive by the surrounding rock, an 

 alteration which he calls endomorphism. 



§ Virlet has attributed the effects of metamorphisra to electro-chemical action ; devel- 

 oped, perhaps, by the aid of high temperature. — [Bulletin dela Societi6 Geologique de France, 

 vol. V, p. 313, 1835.) 



