2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



tution, I visited, in 1907, certain critical districts in the Bernese Alps 

 and was most courteously guided to significant localities in the 

 Diablerets and near Chateau d'Eux by Prof. Lugeon and M. Jaccard. 

 The observations which I was thus enabled to make confirmed my 

 opinion that the visible structures must be essentially those which 

 Prof. Lugeon had described as seen by him, but that his interpreta- 

 tion rests upon mistaken assumptions and is erroneous. The detail 

 of his observations and the painstaking care with which they are 

 made are worthy of the highest recognition, but, in my opinion, the 

 purely hypothetical formula expressed in the conventional figure of 

 a " pli-nappe " is incorrect. 



In the interests of our science, I have sincerely hoped that Prof. 

 Lugeon would explain the structure and movement of the " nappes 

 de recouvrement " as he conceives them, and that his explanation 

 would include such modifications of the accepted theory that it would 

 not contradict the principles of mechanics. Particularly since the 

 publication of the observations of Professor Rothpletz, in the section 

 across Prealpes from Gurnigel to the Wildstriibel, it has seemed to 

 me that the theory of the " nappes de recouvrement," involving the 

 concepts of the " racine," the " carapace," and the " tete," must be 

 justified or corrected. But, so far as I know, no adequate answer to 

 Professor Rothpletz, nor any searching study of the mechanics of the 

 " pli-nappe," has been made. 



There is good ground, in my opinion, to question the following 

 assumptions or inferences of the currently accepted theory of Alpine 

 structure : 



( 1 ) That the overthrust masses of the Alps have all moved in one 

 direction. 



(2) That the so-called " racine " of a nappe de recouvrement is, 

 in fact, the zone of origin of the thrust mass. 



(3) That the supposed " tete" is that part of the structure which 

 has advanced beyond the " carapace " and the " racine " ! 



(4) That the succession of overthrusts in the Bernese Alps has 

 been as described, either in relations of space or time. 



From the observations which I made in 1907, I infer that : 



(i) Overthrusting in the zone of the Prealpes and Bernese Alps 



has proceeded at different epochs from opposed directions : namely, 



earlier from the northwest, later from the southeast. 



(2) The so-called "racine" of the pli-nappe of the Wildhorn- 



Wildstriibel is, in fact, the southern and farthest advanced remnant 



of an overthrust from the northwest. 



