610 MISS M. M. OGILVIE [mRS. GORDON] ON THE [Aug. 1 899, 



Distorted folds in that direction can be traced upon the basis of 

 dip-flexures as follows : — 



1 («) Sella-Pass arch ; (b) Ciavatzes trough and the underthrust on the 



western side. 



2 (a) Arch of the Meisules terrace in the direction from the Meisules to 



the Sella summits ; {b) parallel inward flexure towards the centre. 



3 (a) Pissadoi and Pordoi arch crossing the centre in the neighbourhood 



of the shelter-hut ; (b) diagonal central trough (Jurassic inthrow). 



4 (a) Arch from the Eissee summit to the Eoe summit ; (b) trough from 



the Vallon downthrow inward to the summit-ridge. 



5 (a) Arch of the eastern side ; (b) trough mostly concealed in the under- 



thrust, inward flexures apparent at Cra di Mont and the Campo- 

 lungo Pass. 



6 (a) Main arch across Campolungo. 



It is quite in accordance with our knowledge of crust-movement 

 that a crumpling and contraction of the crust from east and west 

 should succeed a crumpling and contraction from north and south. 

 The whole interest lies in the investigation of the details ; in 

 determining firstly, which was the earlier of the movements in any 

 given area ; secondly, how far the late movements were modified by 

 the pre-existing crust-folds. 



What actually took place in the Enneberg area during the later 

 movement was the subsidence of elliptical areas of the 

 crust, associated with converse torsion-movements in 

 different horizons of the crust. In the areas of sub- 

 sidence, crust-whorl above crust-whorl was arranged 

 in tighter and more contracted positions than would 

 have been possible without torsion-movements. 



Tor si on -buckles. — The presumptive geographical direction 

 and particular local position that would have been assumed by dia- 

 gonal folds if the crust had been more mobile have been determined 

 by the writer not only upon the basis of dip-flexures and diagonal 

 faults parallel with them, but also upon the evidence of series 

 of torsion-buckles. These buckles are distorted periclinal bulgings 

 of the crust at places where diagonal arches of the later movement 

 have interfered with and crossed arches of the earlier movement. 

 The maximum torsion-effects are apparent in the crossing of the 

 chief anticlines in the older system, namely, those of the Groden Pass 

 and Belvedere-Buchenstein. The bulgings are typically lozenge- 

 shaped in ground- plan, with a longer axis in some oblique east-and- 

 west direction, and a short axis in some oblique north- and-south 

 direction, but not rectangular to the other. 



As an example, take the torsion-buckle at Plon, on the west of 

 the Groden Pass (see map, PI. XL). The diagonal north-north-east 

 and south-south-west arch across the Sella Pass has intersected 

 there the Groden-Pass Anticline, and the effect has been the de- 

 termination of a local centre of crust-weakness and cross-ruptures. 

 The chief crust-rupture has occurred along (a) the west side of the 

 diagonal arch, and is marked by an intrusive dyke. (6) Oblique 

 torsion- faults are associated with the chief ruptures ; they form 

 two opposite virgating bundles, the one converging eastward 



