﻿Yol. 64.] ANNIVER8AEY ADDRESS OP THE PRESIDENT. U 



was led into that special tectonic domain where he achieved his 

 fame and did most signal service to the cause of geological science. 

 The Jura Mountains had long been classic ground, on account of the 

 striking examples which they present of simple anticlinal and 

 synclinal folding. This structure is most conspicuously displayed 

 in the higher or Swiss portion of the chain. But Bertrand found that, 

 as the folded strata extend into French territory, their folds become 

 complicated with faults. As he contemplated this marked differ- 

 ence of structure, which he was convinced must be a part of the 

 general process of mountain -makiug, he asked himself whether 

 the fold and the fault should be looked upon as features independent 

 of each other, marking different movements and arising from distinct 

 causes. The longer he pondered over this question, the more funda- 

 mental it became in his eyes. To quote his own words : — 



' The idea of making a fault a subject of study and not an object to be merely 

 determined has been the most important step in the course of my methods of 

 observation. If I have obtained some new results it is to this that I owe it.' ^ 



He not only recognized the normal relations between plication 

 and fracture, but on the margin of the Jura chain, around Besangon 

 and Salins, he discovered the existence of nearly horizontal faults 

 whereby the older had been driven over the younger formations. 

 These displacements were indeed of small magnitude, but it was the 

 first time that they had been observed in Prance, and they must 

 always possess an historic interest for the influence which they 

 had in directing Bertrand along the path that led to his later 

 generalizations.^ 



The next stage in the evolution of his ideas regarding the 

 character and origin of mountain-structure was gained as the 

 result of an attentive study of Prof. Heim's description of the Glarus, 

 and a comparison of the published sections of that mountain with 

 those which Prof. Gosselet and others had given of the Franco- 

 Belgian coal-field. In 1884 he communicated a paper on this 

 subject to the Geological Society of Prance, wherein he affirmed 

 that, in place of Prof. Heim's ' double fold,' there stretches from 



^ ' Notice sur les Travaux Scientifiques de M. Marcel Bertrand ' 1894, being 

 a statement of his work prepared by himself for the information of the Academy 

 of Sciences when he was a candidate for election into that body. In preparing 

 the present Obituary Notice I am much indebted to this interesting auto- 

 biographical tract, a copy of which has been kindly lent to me by my friend 

 M. Emmanuel de Margerie. 



^ His account of this discovery was published as far back as 1881, in the 

 Bull. Soc. G60I. France, ser. 3, vol. x, p. 114. 



