56 PROF. T. G. BONNET ON THE [Feb. I903, 



I think that some details in this statement may be rendered more 

 precise, and have no belief in the existence of a zone of ' pietre 

 verdi ' as a definite geological horizon. As I have elsewhere shown, 1 

 these green, more or less actinolitic schists are most abundant in 

 the group which 1 have designated for purposes of reference ' the 

 upper schists.' The latter vary from dark mica-schists, but slightly 

 calcareous, and occasionally containing garnets, staurolites, etc., 

 to nearly pure marble on the one hand, and to quartz-schists on the 

 other. Among these the green schists are often abundant, being- 



Fig. 1. — Position of the FiJon Licone. 



[Diagrammatic sketch from the Vallon de Valeiglia.] 



1, 2 = Certainly calc-mica-schist, probably going to the top of the bill above 1. 



3 = Serpentine, the limits being made fairly distinct by the colour of the rough 



hillside due to small outcrops; it seemed to thicken towards the left. 

 The + indicates the position of the mine. 



4 = Probably calc-mica-schist ; there is possibly a small outcrop of serpentine 



at -v — *-. 

 Beneath -v- is a ravine which runs up. dying out, rather to the right of 

 the mine. 



not seldom clearly intrusive. 2 Similar rocks also occur, though 

 more rarely, among the underlying gneisses, so that, at any rate in 

 most parts of the Alps, the green schists are pressure-modified 

 diabases, generally intrusive in the calc-mica-schist group, the 

 serpentines being also intrusive, sometimes into the one, sometimes 

 into the other. 



The appended diagram, fig. 1 (made from the lower part of the 

 Yallon de Yaleiglia), rough as it is, may save a long description. 

 The iron-ore is clearly associated with a mass of serpentine, above 

 and below which are thick masses of calc-mica-schist. Over these, 

 which became in one part almost a pure marble, we walked in 



1 Quart. Journ. Geol. Soc. vol. xlii (1886) Proc. p. 55, vol. xlv (1889) p. 97, 

 vol. xlix (1893) p. 94, & vol. 1 (1896) p. 279. 



2 Almost all show the effects of pressure, some to a very great extent. This 

 also frequently spoils junctions. In one instance (in the Tyrol) I suspected a 

 passage, but I should like to examine this again in the light of later experience. 



