1 68 SCIENCE PROGRESS. 



series of ridges which run approximately north and south. 

 The ridges are due to folds. The geological structure of 

 the massif is much like that of the others in this district. 

 It has been described as consisting of a central coarse 

 gneiss ; then a zone of amphibolic gneisses ; and then an 

 upper series of mica-schists. These are referred to the 

 Archean. Above this is a great gap, and the series of 

 deposits recommences with the Carboniferous. Triassic 

 dolomites and Jurassic limestones complete the series. 



There is therefore a close resemblance between the 

 general stratigraphy and that of the ordinary Cottian 

 sequence, and when we come to details the resemblances 

 are increased, and there are facts described which support 

 the views of the last paper. Thus the supposed central 

 gneiss is described in one case — the " Massif des Sept 

 Laux " —as an eruptive granulite. Moreover, the coarser 

 mica-schists are described as injected with granulite veins. 

 So that we have here a quite independent confirmation of 

 the view that some of the "central gneisses" of the 

 Western Alps are intrusive in their character. 



The date of the intrusions is left undecided. M. 

 Termier thinks they are probably of different ages (p. 33). 

 The dolomites seem to resemble those of Monte Chaberton, 

 but they are unfossiliferous; their age is therefore only deter- 

 mined by their position between the Carboniferous and the 

 Lias. 



The Carboniferous rocks are of interest from two 

 points. In the first place, they contain a great number of 

 beds of trachyte (or orthophyre, as it is of course called 

 by the author). The site of the volcanic centres through 

 which these were erupted is discussed in the monograph. 

 In the second place, the metamorphism of the Carboniferous 

 beds is fully considered. On p. 8 we are told that the Car- 

 boniferous beds are in places very difficult to distinguish 

 from the Archean schists. M. Termier has, however, sub- 

 jected them to careful examination under the microscope, 

 and says that this method enables them to be distinguished 

 at once (p. 43). 



The last chapter in the work discusses the folds and 



