﻿588 ME. E. B. BAILEY ON EECTJMBENT EOLDS IN THE [Nov. I9IO 



his British colleague Prof. Lapworth. During the years in which 

 the latter was largely concerned in unravelling the facies problem 

 presented by the Southern Uplands of Scotland, Bertrand was per- 

 forming a like task in the Jura mountains, following the lead there 

 given by 'le " sauvage " mais genial Gressly de Soleure.' Both 

 Lapworth and Bertrand in the course of their researches were thus 

 introduced at about the same time to the complications incident 

 upon small-scale isoclinal folding and reversed faulting. Then 

 turning to new fields of enquiry in 1882, both investigators came 

 face to face with the phenomena of large-scale overthrusting, the one 

 in the North-West Highlands, the other in Lower Provence [10]. 



The inconstancy of facies of sedimentary groups, which early 

 attracted the attention of both Lapworth and Bertrand, has up 

 to the present proved nothing else than an impediment in the 

 development of tectonic ideas so far as Britain is concerned. In 

 Alpine regions, however, this apparent difficulty has been, not so 

 much surmounted, as actually turned to advantage. Suess [11] 

 in 1875 contrasted the sediments, driven forward to build the 

 outer folds of the Eastern Alps and Carpathians, with their time 

 equivalents, where such exist, in the over-ridden foreland regions 

 beyond. Bertrand, too, in his well known paper of 1884 [12], 

 alluded to the Alpine (as opposed to Helvetian) facies of the 

 Rhaeticon thrust-mass lying in front of the Alps. Suess and 

 Mojsisovics [13] had previously recognized the marginal super- 

 position of the Rhaeticon Alp on the neighbouring masses of 

 Helvetian facies, but interpreted this relation by faulting and back- 

 folding: Bertrand saw in it evidence that the entire Rhaeticon is 

 a masse or lambeau de recouvrement. His object in writing 

 this paper was to extend the notion of large-scale thrusting to the 

 solution of Alpine problems in general. He indicated that the 

 blocs exotiques of the Alps maybe fragments of nappes de 

 recouvrement, and in especial he gave a new interpretation on 

 more generous lines of the wonderful Glarus inversion, so long 

 rendered famous owing to' the researches of Escher and Heim. 

 Bertrand's suggestions were neglected by Swiss geologists for many 

 years, probably because he had not seen for himself the Glarus 

 Rhaeticon, and other sections which he thus boldly re-interpreted. 



In 1892 Bertrand [14] visited the North-West Highlands in the 

 expectation, he tells us, of finding that an important difference of 

 detail, distinguishing the sections drawn by Dr. Peach and Dr. Home 

 from those with which he was himself familiar in the exposures 

 of the Alps and Provence, would vanish on closer enquiry. The 

 feature which at the time seemed so peculiar in the North-West 

 Highland thrusts was the complete suppression of the lower in- 

 verted limb of each recumbent anticline to which, according to 

 Prof. Heim's idealization, the various individual thrusts should 

 correspond. 



Bertrand found that this difference was real so far as research had, 

 at that time, revealed the structure of the two countries compared. 





