164 SCIENCE PROGRESS. 



In Zaccagna's paper we also have to regret the absence 

 of more detailed petrographical descriptions of the rocks, 

 and especially of those assigned to the Permian. Into the 

 general question of the sedimentary sequence described by 

 this author we need not follow him, except in two points. 

 He remarks that he assigns to the Trias "all the compact 

 and brecciated limestones, . . . which Lory in his map con- 

 sidered as the Alpine type of his Lias compacle, or Lower 

 Lias, and grouped under the name of the ' Calcaire du 

 Brianconnais ' ". Further, he believes that a break occurred 

 in the deposition of beds between the Trias and the 

 Jurassic. The latter of these points appears to be estab- 

 lished by the author, but in the former he probably goes to 

 an extreme. 



A third paper (8) issued last year also deals with the 

 main problem considered by Zaccagna and Bertrand, viz., 

 the age and relations of the three members of the schist 

 series. It announces conclusions totally different from 

 those of these two authors. The paper describes the 

 country to the south and south-east of that considered by 

 them, with the exception of a branch excursion to the 

 Paradiso. This author has concentrated his attention on 

 the u central or basal gneisses". 



These had been represented as a continuous line 

 running from north to south, parallel to the main chain, 

 and as being the oldest rocks in the Alps. The author, 

 however, now maintains that they are nothing of the sort ; 

 that they are a series of isolated independent masses, and 

 occur at no one fixed horizon in the series ; that instead of 

 being altered sediments lying at the base of the series, they 

 are igneous rocks intruded into the schists. The evidence 

 adduced in support of this rather startling change of view 

 is of six kinds. If the gneisses had been the oldest rocks, 

 and the others had been deposited upon them, we should 

 expect to find fragments of the gneiss in the beds above 

 them. Gritty and pebbly beds occur in the overlying 

 schists, but there is among them no trace of materials 

 derived from the gneiss. On the contrary, there occur in 

 the gneiss near its margin included fragments of the over- 



