226 Notices of Memoirs — Prof. Bertrand — Structure of Alps. 



side incline towards Italy, and all those on the west towards 

 France.^ 



The exceptions to this rule, such as the fans of Mont Blanc and 

 St. Gothard, are infrequent and accidental. Side by side with 

 classic sections of these massifs, which show fan structure, I 

 believe that one could cite others, parallel, where it is wanting. 

 Besides, such exceptions are only to be seen on the flanks of the 

 " araygdaloidal massifs," to which I shall shortly refer.^ 



Towards the north-east on reaching the (Swiss-Italian) frontier 

 the central zone swells out considerably, so as to embrace the whole 

 Monte Bosa massif; in this broadened zone the folds are not inclined 

 in any one determinate direction. 



On the south the zone undergoes a more extraordinary change ; 

 instead of being occupied, as seems natural, by the most ancient rocks 

 arranged in an anticlinal, it is made up of the most recent rocks, 

 the nummulitic beds, and the flysch. The central zone is marked, 

 geologically speaking at least, not by an uplift but by a depression. 

 A preliminary note by MM. Kilian and Haug has told us that in 

 this new region (nummulitic band of Ubaye) there seem to be 

 peculiarities altogether unique in the Alps — inclined folds of pre- 

 Eocene date. Possibly these peculiarities can be correlated with 

 the great and sudden lowering of the central zone of the fan. 

 However that may be, the Eocene band, from the point of view of 

 the inclination of the folds, certainly plays the same part as the 

 Carboniferous belt; all the western folds incline towards France, 

 all the eastern ones towards Italy. Moreover, further on, the 

 Mercantour massif, lising within the Eocene belt, marks a tem- 

 porary return to a sharply anticlinal form. It seems to me, on 

 comparing the folds of which the bearing is known in the inter- 

 vening region, that the centre of the Alpine fan corresponds exactly 

 with that of the Pyrenees. 



(2) The plan of the folds in this part of the Alps shows an 

 " amygdaloidal or beaded structure " (une structure amygdaloide 

 ou en chapelets), that is, the folds, while following the general 

 trend of the chain, open out here and there round elliptical lenticles, 

 themselves broken by new folds which have the same direction but 

 are not prolonged beyond them. The system thus presents a series 

 of nodes and ventral segments comparable with the foliation of an 

 augen (amygdaloide) gneiss, in which the folia bend round great 

 kernels (noyaux) of quartz and felspar. 



To give an idea of the importance of such kernels I will cite first 



1 It is by virtue of this fan structure that the relatively recent date of the 

 "lustrous schists" can be demonstrated. Throughout almost the entire range of 

 these schists order of superposition proves nothing, because the structure is uniclinal. 

 Fortunately certain great patches are still left on the summit of the fan. Thus not 

 only is evidence of superposition perfectly clear, but it is such as to allow no other 

 interpretation. 



2 There would be, it is true, an important exception if the massifs of Annes, the 

 Chablais, the Faulhorn, and the north fold of Glarus are, as is usually maintained, 

 true anticlinal masses. This exception would disappear if they are overthrust masses. 

 Thanks to the work of M. Schardt, attention is now definitely drawn to this 

 problem, which I believe to be on the eve of solution. 



