158 SCIENCE PROGRESS. 



"Description geologique du Dauphine " (i 861-1864), st iU 

 ranks as one of the most important works on Alpine 

 geology. For many years, under the influence of Lory's 

 teaching, this view was almost universally accepted. Those 

 who, like Gastaldi, rejected it were actuated mainly by 

 theoretical considerations. In 1887 and 1889 two protests 

 against this view were made after a careful examination of 

 typical sections across the Cottian Alps. These were 

 issued by Signor Zaccagna and Professor Bonney. They 

 showed that the schists underlay the Triassic rocks uncon- 

 formably, and must therefore be pre-Triassic. They regard 

 them as very much older than the Trias, and assign them 

 to the Archean. Their evidence seemed incontrovertible, 

 and has been supported, at least in affirming the pre- 

 Triassic age of the schists, by Mr. A. M. Davies and the 

 present writer. 



Now, however, M. Bertrand, who had previously an- 

 nounced that Lory's view must be abandoned, has gone 

 back to the old idea of the Triassic age of the schists, and 

 especially of that part of them known as the ''schistes lustres". 

 The reasons for this reactionary step are stated in two 

 papers, which are issued together as " Etudes dans les 

 Alpes Franraises ". The first describes the arrangement 

 of the main structural lines in the country and their relation 

 to the great igneous masses, and the metamorphism 

 which the rocks have undergone. The second describes 

 the " Schistes lustres de la zone Centrale," and discusses 

 their age. It is really the latter subject that is the more 

 important, and the one which may be the more easily 

 settled. 



Bonney and Zaccagna have shown that in some places 

 the "schistes lustres" are unconformably overlain by the 

 basal beds of the Trias, or even Permian. The former 

 author has given a section of the Pass of Mount Genevre, 

 the accuracy of the facts in which M. Bertrand does not 

 question. It appears as if this one section is quite sufficient 

 to settle the relative age of the two series. Bertrand, 

 however, denies this, and says we must rest our conclusion 

 on the general evidence of all the sections in the district. 



