MECHANICS OF FORMATION OF ARCUATE MOUNTAINS 75 



years of study in the region, that though in certain favored dis- 

 tricts maps and sections reveahng internal structure may be pre- 

 pared, for the larger portion of the region the most that can be 

 expected is to derive a general notion from the study of the key 

 localities. 



The blanketing series of slices which make up the Alps. — It is 

 not our primary purpose to present in detail at this time the 

 modern Swiss interpretation of Alpine structure, or the objections 

 which have been raised against it. Such an outline, important 

 as it is for American students, who are likely to be bewildered by 

 the many new terms, particularly when these terms are found in 

 the original German and French sources, must be deferred until 

 after the mechanics of the process has been considered. It is 

 perhaps sufficient to allude here to the fact that the conception 

 of series of blanketing slices {Decken or nappes de recouvremeni) , 

 which originated in the mind of Bertrand in 1884,^ was worked out 

 independently and applied by Schardt in 1890-93 in the Voralpzone, 

 and again by Lugeon in 1896, has now overcome all opposition in 

 Switzerland, and, following its adoption by Heim himself in 1903, 

 it has been the accepted doctrine of all Swiss workers without 

 exception. 



The story of the gradual acceptance of this theory reads like 

 a romance and probably has no parallel in the history of geology. 

 When the idea was first suggested by Bertrand upon the basis of 

 his studies of the coal basin of northern France, no one seems to 

 have taken the theory seriously as it applied to the Alps, since its 

 author had never studied that region upon the ground. When 

 nine years later Schardt was independently forced to similar con- 

 clusions in order to explain the structure within the area between 

 the lakes of Geneva and Thun, he was vigorously opposed, by 

 Lugeon among others. Hardly three years later Lugeon had been 

 forced by his own studies to accept the new doctrine, and he is now 

 its most prominent champion. Heim himself, whose name for 

 almost a generation had been identified with the earlier theory 

 of the double fold, accepted the new theory in 1903, and thereafter 



^Marcel Bertrand, "Rapports de structure des Alpes de Claris et du bassin 

 houiller du Nord," Bull. soc. geol. de France (3), XII (1884) 318-30, PI. 11. 



