324 MESSES. G. A. J. COLE AND J. W. GREGORY 



bear in mind that, even at the present day, there are numerous 

 authors who would question their erui3tive origin. Scipion Gras* 

 in 1844 went so far as to assert that dykes and veins were unknown 

 in connexion with the variolites, spilites, euphotides, and serpentines 

 of the Alps, which in Dauphine and Savoy " particularly affect the 

 anthracitic formation." A more detailed examination of the base 

 of Le Chenaillet, however, would probably have modified this 

 opinion. When the French Geological Society visited the area in 

 1861, M. Hebertt, supported by M. Studer, maintained that the 

 compact rocks seen on the east side of the Yal de Gondran (i. e. the 

 variolitic diabases) were nearly horizontal sediments which had been 

 metamorphosed by injections of serpentinous matter. This view, 

 however, was strongly opposed by Lory, and was certainly held by 

 only the minority of the members present in the field. We have 

 already referred to the opinion of some geologists as to the stratified 

 character of various " pietre verdi." It is not for us to enter into 

 the vexed question of the origin of serpentine and euphotide or of 

 other " greenstones " ; and we must content ourselves with a passing 

 reference to some of the more recent literature on this subject, 

 selecting papers that deal with the area of the Apennines and the 

 Alps. 



Prof. Bonney J, for example, has carried his studies on serpentine 

 as far as the masses of Liguria, and strongly insists on their intrusive 

 character. He also opposes the view that serpentine can be derived 

 from gabbro. In 1880 Issel § criticized these opinions, and shortly 

 after published, with Mazzaoli jl, a paper in which it is suggested 

 that the serpentines were poured out as a warm impalpable mud on 

 the sea-floor, where they underwent slow internal changes through 

 the action of vapours and liquids. The authors hold that such 

 changes would be competent to produce the diorites, euphotides, 

 granitones, and variolites so constantly associated with the ser- 

 pentines. Lotti ^, on the other hand, acknowledges and helps 

 to demonstrate the igneous origin of euphotide, and recognizes this 

 rock as the deep-seated type of diabase and basalt. But he differs 

 from Prof. Bonney w^hen he asserts that serpentine may be derived 

 from ordinary basic rocks by alteration, through the permeation of 

 magnesian waters from below. 



In connexion with this point it will have been seen that the 

 apparent passage from altered gabbro to serpentine at the Col 

 du Gondran is deceptive, and that we regard the serpentine as 

 resulting from an exceptionally basic mass formed in intimate 

 association with the normal and felspathic igneous rock. 



* "Constitution geologique des Alpes centrales de la France et de la 

 Savoie," Bull. Soc. geol. France, 2^ ser. t. i. p. 723. 



t Bull, Soc. geol. France, 2<= ser. t. xviii. p. 782. 



J "Notes on some Ligurian and Tuscan Serpentines," Geol. Mag. 1879, 

 p. 3()2. 



§ Boll. R. Oomit. geol. d'ltaha, vol. xi. p. 183. 



•|| "Relazione degli studi fatti per un rilievo delle masse ofiolitiche uella 

 riviera di Levante," ihicl. vol. xii. (1881) p. 313. 



^ " Contribuzione alio studio delle serpentine italiane e della lore origine," 

 ihid. vol xiv. (1883) p. 281. 



