6 SCIENCE PROGRESS. 



description is given of the Precambrian rocks, consisting of 

 hornblendic gneisses, amphibolites, and mica-schists (both 

 granulitic and non-granulitic). Carboniferous rocks (gres 

 a Anthracite) appear on each side of the principal ridge in 

 the form of two regular synclines (an eastern and a western), 

 which seem to correspond with two separate basins occupy- 

 ing depressions on each side of a precarboniferous chain. 

 Some of these Carboniferous beds have suffered consider- 

 able metamorphism, and the author gives petrological de- 

 scriptions of the macroscopic and microscopic characters 

 of a number of new types of these metamorphic rocks, in- 

 cluding highly altered conglomerates, sandstones, etc. In 

 most cases sericite is the only new mineral produced by the 

 metamorphism. Orthophyric volcanic rocks are described ; 

 stratigraphical observations lead the author to consider that 

 most of the lavas occur at the top of the Carboniferous 

 deposits of the Grandes-Rousses Massif. A description of 

 the systems of folding is given, the Hercynian folds run 

 generally north and south, as does one set of the Alpine 

 folds, whilst another set of the latter runs east and west. 

 The paper is a valuable contribution to the effects of 

 dynamic action in producing metamorphism of recognis- 

 able sediments. 



Taking now into account the papers treating of special 

 deposits or groups of deposits, we do not find many dealing 

 with important questions concerning Precambrian rocks. 

 Bell (7) describes some remarkable outliers of Potsdam 

 beds and Black River limestones in depressions of granite. 

 He suggests that these depressions are due to submarine 

 weathering. Much of the Archaean rock must have been 

 denuded before the deposition of the Palaeozoic rocks upon 

 it, and the interval between them is considered to have 

 been probably much greater than has generally been sup- 

 posed. It is to be observed, however, that the presence of 

 Black River beds immediately succeeding Precambrian 

 rocks, indicates further weathering of these rocks in 

 Palaeozoic times before the deposition of the Black River 

 limestone. 



Wiman (8) describes as organic a problematical body 



