i62 SCIENCE PROGRESS. 



tion of true schists and Triassic limestones. M. Bertrand's 

 arguments do not, however, carry conviction on either 

 point. The fact that in several sections the schists occur 

 in immediate contact with the Trias (as shown by Bonney, 

 Diener, Cole, Davies and the writer) and that the two 

 then show no approximation in characters is opposed to 

 the former; while the fact that M. Bertrand makes no effort 

 to employ petrographical methods shakes one's faith in 

 his identification of the last. It is no use criticising- M. 

 Bertrand's views without an examination of his principal 

 sections on the ground. For he admits that the best 

 known sections in which the facts are beyond dispute 

 present serious difficulties to his hypothesis. He evades 

 these, however, by stating that sections which are not so well 

 known are so absolutely conclusive as to the truth of his 

 views that we must dismiss the others as exceptional and 

 misleading. 



Another long memoir describing exactly the same 

 district has been issued by Signor Zaccagna (7). It is 

 illustrated by a map covering almost the same area and 

 on a scale of a third larger than that of M . Bertrand's, and 

 also by a series of sections which run along much the same 

 lines. The facts shown on the maps and the conclusions ex- 

 pressed in the memoirs are almost as different as they can be. 

 Whereas M. Bertrand denies that there are any rocks in 

 the district older than the Permo-Carboniferous, Siomor 

 Zaccagna represents more than half of it as Precambrian. 

 According to the former the central coarse-grained gneiss 

 of the Paradiso is an altered Carboniferous sediment ; the 

 latter makes it the oldest member of the Archean. Where- 

 as the former regards the " schistes lustres" as altered 

 Trias, the latter refers it to the upper member of the 

 Archean. Signor Zaccagna therefore reaffirms for the 

 Central Grains the conclusions announced for the Western 

 Alps in general by himself and Professor Bonney. 



Zaccagna's work appears to be a careful and detailed 

 piece of field-work. The map is of course only a small 

 scale sketch, and the sections appear in places to be only 

 diagrammatic. We should be inclined to dispute the 



