All earlier studies of folded mountain ranges ignored the relationship between plan and cross-section or profile. Largely in consequence of this neglect, the forces to which they have been supposed to owe their structure have been assumed to possess a bilateral symmetry. For the classical area of the Alps, the folded region which has been studied for the longest time and in the greatest detail, this idea of bilateral symmetry was expressed in the words of Escher and his pupil Heim as zweiseitigen Druck.
It was Eduard Suess who as early as 1875, in his Die Entstehung der Alpen, by focusing attention on the plan, rather than the profile, of mountain ranges, showed that an asymmetrical arrangement of the ranges within definite arcs called for an asymmetrical disposition of the forces which had produced them. Very shortly thereafter James Dana, in . . .