Reviews — Geological Survey of Scotland — Geology of Cowal. 85 



the evidence of the contained fossils, to be much newer, and to 

 be in fact the equivalents of the lower portion of the Trenton 

 formation ; and to this horizon may also now be assigned the greater 

 portion of the strata in the city of Quebec. Here, however, there 

 are a number of anticlinal folds, and the presence of certain fossils, 

 similar to those obtained from the Levis beds, indicates that along 

 some of these folds beds of that horizon may be found. The same 

 age may be assigned to the great extension of the black slates 

 and limestones which occur at intervals along the south shore of 

 the St. Lawrence, nearly to the extremity of the Gaspe Peninsula, 

 and which appear to dip beneath the strata of tke Sillery formation 

 at many points. 



In regard to the use of the term Potsdam a distinction must now 

 be made between the Potsdam formation and the Potsdam Sand- 

 stone. The latter has been clearly proved in Canada to be the lower 

 portion of the Calciferous formation, and is not separable from it, 

 while there is a manifest break between this and the lower beds, or 

 the Cambrian proper. The term Potsdam formation in Canadian 

 geology was a comprehensive one like the term Cambrian, and 

 like it included all between the Calciferous formation and the 

 Huronian. The discriminate use of the terms has led to much 

 confusion, and as the divisions of the Cambrian have now been 

 properly determined the expression Potsdam formation has practi- 

 cally no meaning in Canadian geology. 



la IE "V I E "W S. 



Memoirs of the Geological Survey, Scotland : The Geology 

 OF Cowal, including the part of Argyllshire between the 

 Clyde and Loch Fine. By W. Gunn, F.G.S., C. T. Clough, 

 M.A., F.G.S., and J. B. Hill, E.N. ; with Petrological Notes 

 by J. J. H. Teall, M.A., F.R.S., Sec. G.S., and Dr. Hatch, 

 Ph.D., F.G.S. 8vo ; pp. 333, with index, numerous illustrations 

 in the text, and ]0 plates. (Edinburgh : Neill & Co. Price Gs.) 



THE Director-General of the Geological Survey observes, in his 

 Preface to this Memoir, that the district known as Cowal 

 " embraces the south-western extension of the various bands of 

 metamorphic rocks which form the southern edge of the Highlands. 

 Bounded on three sides by coast-lines, and penetrated by a number 

 of sea-lochs, it affords better and more continuous sections of these 

 rocks than are generally to be met with in the interior of the 



country From the detailed study of this part of the 



Highlands much information has been obtained by the Geological 

 Survey regarding the structures of the schists and the successive 

 movements by which these structures have been produced. Originally 

 most of the rocks described in the following chapters formed a thick 

 series of sedimentary deposits, the geological age of which still 

 remains to be determined. These strata have been found to have 

 undergone a remarkable series of repeated movements. After being 

 thrown into folds and having been cleaved so as to acquire a first 



