604 MISS M. M. OGILVIB [mrS. GORDON] ON THE [Aug. 1 899, 



massive, namely, the Pissadoi Eavine, north-north-east aud south- 

 south-west, and the Yal la Stries Kavine, directed east and west. 



Torsion-phenomena on the eastern side. — The strike of 

 the strata, and the overthrusting in the peripheral fold, curve round 

 an eastern arc from the Groden Pass to the Cordevole Y alley. The 

 actual change of direction takes place at a sharp angle in the neigh- 

 bourhood of Pian de Sass, and the influence of conflicting force- 

 components at this part so far explains the confused position of the 

 rocks. JS'orth of Pian de Sass the shear-planes diverge north and 

 north-west ; south of Pian de Sass they converge south-west towards 

 the Bova Alp. While the overthrusts may be taken in themselves 

 as a proof of lateral compression, the curvature of the shear-planes 

 is a proof that the lateral compression was combined with horizontal 

 torsion. 



Purther evidence of the crust-torsion is afforded by the presence 

 of vertical faults radiating outward from the inner areas of Sella 

 in north-easterly and south-easterly directions, and therefore inter- 

 secting the shear-planes. These faults are transverse to the several 

 tangential shear-slices which compose the complete torsion-curve, 

 and may be termed torsion-radii. 



The chief rock-joints also form a radiating series on the east 

 side, radiating to north-east, east, and south-east. They stand 

 undoubtedly in torsion-correlation to an opposite series of fissures 

 and slight faults which radiate from the higher horizons of Cher/ 

 Hill to the north-west, west, and south-west, round the Campo- 

 lungo curve of the hill. 



The Sella Series and the Cherz Series are separated by the 

 Campolungo Pault, which limits the Sella synclinal area on the 

 east side. On the downthrow or west side of the fault the Wengen- 

 Cassian strata are tilted westward, and the strike is twisted to 

 north-west and south-west. On the east or upthrow side there is a 

 decided dip-flexure from west (facing Sella) to north-east (facing 

 Pralongia), and the strike twists to north-north-east and to east- 

 south-east. 



The Campolungo Fault therefore traverses a diagonal anticline 

 directed north-north-east and south-south-west, and dividing the 

 deep Sella basin from the shallower syncline of Pralongia. The 

 diagonal fault is met on the west side by curved torsion-faults from 

 the two main east-and-west anticlines on the north and south, and also 

 by torsion-radii diverging outward from the adjacent basins. These 

 faults and curves are so intimately associated with the diagonal 

 anticline that the latter is comprehensible only as the expression 

 of a vertical movement contemporaneous with horizontal movements 

 of torsion. 



Cleavage-planes penetrate the rocks of the mountain, generally 

 speaking, in two directions, north-north-west and south-south-east, 

 and north-north-east and south-south-west. Pound the eastern 

 curve of the mountain, however, the arrangement is specialized in 

 accordance with the sharp curvature and strong compression on 

 this side. North-and-south cleavage-planes pass through all the 



