ON THE FORMATION OF CRYSTALLINE ROCKS. 247 



The remarks of Longchamp on the relation between the thermal 

 springs of Chaudesaigues and the lode of iron pyrites from which 

 they spring*, and on the other hand, the ingeniaiis experiments by 

 which Becquerel was able by the humid process to imitate galena, 

 sulphuret of antimony, and other minerals of metallic veins, contri- 

 buted to recall ideas in this direction.t Since 1833, Fournet, 

 after having studied the metallic veins of Pontgibaud, in Auvergne, 

 concluded that they had probably been filled by the incrustations of 

 mineral waters.:}: The raineralogical resemblance between the veins 

 of Saxony and the silicious and metalliferous deposits of the lias, in 

 Bourgoyne, which, according to all probability, could only have been 

 made in the wet way, confirmed this opinion, as has been shown by 

 Baron de Beust.§ Besides, as Elie de Beaumont had a long time 

 before said, in his lectures at the School of Mines, || metallic veins are 

 generally found near lines of contact of the stratified with the un- 

 stratified rocks which have penetrated them; and such is also the 

 usual position of hot springs, which at the present time very fre- 

 quenth^ deposit stony or metallic substances in the channels through 

 %vhich they run. The important conclusion to which this collation of 

 facts led, on the mode in which metallic veins have been filled, dif- 

 fered in essentials still more from the hypothesis of Werner, than 

 from those of Descartes and of Hutton. 



Moreover, the study of the metamorphic formations themselves 

 brought to light circumstances which the dry process could not ex- 

 plain, and especially the extent and uniformity of the transformed 

 masses, the mode of dissemination, and the arrangement of the mine- 

 rals which were formed in these rocks, which were ascertained not to 

 have been softened and never to have been submitted to a very high 

 heat. This last induction results from different facts which will be 

 noticed in the third part of this work. 



Durocher, in the sequel to a memoir published in 1846,^ where 

 he recorded many observations of his own, attributed the effects of 

 metamorphism to slow action and to molecular transference very anal- 



- Annales de Chimie et de Physique, vol. xxxii, p. 294, 1826. 



■\ Annales de Chimie et de Physique, October, 1829 ; September, 1832 ; May, 1833. 



X Bulletin de Ui SccietiS Geoloc/ique de France, vol. v, p. 188 — vol. iii, p. 2.ol. 



In 1837 Mr. Robert Were Fox (Report (if the Royal Cornwall Polytechnic Society for 1836) 

 showed how lodes appear to owe their origin to hot springs ; he attributed their forma- 

 tion to thermo-electrical effects — the traces of which he thought he had found in the ex- 

 periments he had made on metallic veins. 



De la Beche adopted these ideas in his Geological Report on Cormmdl and Devon, 1839. 



^ Kriiische Beleuchluny der Wernerschen Ganythwrie, p. 6, 1840. — The author points out the 

 striking resemblance of the deposits contained in the beds of ariiose of liurguud)^ with the 

 veins of Freyberg. 



The interesting observations of Biscliof on tlie formation of iron pyrites and on hot 

 springs have contributed to confirm this result. The memoir which he published on the 

 filling up of metallic veins, bears date 1843. — (Ueber die Entstehung des Quarzes tind Erz Giinge.) 



li Explication de la carte Geologique de France, vol. 1, p. 43, 1841. 



•y Etudes sur le metamorphism. Bulletin de la Society Geologique de France, 2d series, vol. 

 iii, p. 547, 1846. Metamorphism dans les PyrentJes. — (Annales des Mines. 3d series, vol. vi. 

 p. 78.) 



