﻿530 Geological Society : — 



the Alps, was completed in April 1905 ; but, acting on the advice 

 of Sir Archibald Geikie, the authoress has since endeavoured to 

 strengthen her line of argument by taking as a type the series of 

 structural changes undergone in the largely-igneous mountain- 

 massive of Bufaure in the Dolomites, and elucidating the successive 

 phases from the point of view of historical geology. 



After describing in detail the geology of the Bufaure Massive, 

 the authoress discusses the structural relation of the Western Alps 

 and the Engadine to one another and to the whole mountain- 

 system. From the particular arrangement of overthrusts, as well 

 as from the distribution of the igneous intrusions in the Western 

 Alps and in the Engadine, the authoress concludes that these were 

 areas where leading cross-faults intersected the east-and-west Central 

 Alpine band, and shows how the coalescence of these cross-faults 

 with E.N.E.-W.S.W. faults on the north side and W.N.W-E.S.E. 

 faults on the south side defined two leading fault-curves, the one 

 passing through the Engadine and continuing in the Dalmatian 

 Alps, the other passing through the Western Alps and continuing 

 in the Apennines. These strike-curves are essentially peripheral to 

 the western side of the Hungarian Basin. 



The cross-segment comprising the Rhine-Ticino district between 

 the Western Alps and the Engadine is, according to the authoress's 

 interpretation, anticlinal in character, segments having been down- 

 thrown from it both towards the west and towards the east, and 

 overthrust masses having crept eastward and south-eastward from 

 the Western Alps, and westward from the Engadine. 



The authoress then discusses the relation of the French Jura 

 Mountains to the Alpine System, pointing out that the Swiss-French 

 Plain flanking the Western Alps presents the same essential features 

 of structure in relation to the Western Alps on its east side and the 

 French Jura Mountains on its west, as those that she has elucidated 

 for the Ehine-Ticino cross-segment. She consequently interprets 

 the strike-curve round the west formed by the Jura Mountains and 

 the ranges of Dauphin e as the outermost peripheral plication al 

 system in the Alps, showing that the whole region between the 

 Hungarian Basin and the ancient mountain-groups of Central 

 France has been under the influence of the westward thrust. 



The general principle of structure treated of above — namely, the 

 sagging of crust-blocks by means of normal faults towards bands 

 or localities of crust- weakness or subsidence, and the reverse or 

 overthrust-movements which may take place from within these 

 bands or localities — is that which the authoress demonstrated in 

 the Dolomite-Massives in 1893, and has ever since advocated as a 

 leading principle in the interpretation of Alpine structures, the 

 important consideration being that where, as in the Alps, the 

 principle is applicable in relation to two intersecting axes of 

 deformation, the phenomena produced must necessarily be of the 

 nature of ' interference-phenomena.' 



A leading feature of the paper is the evidence that it affords of 



