568 



ME. G. W. LAMPLTJGH ON THE 



[Nov. 1895, 



western side of the central axis, where the prevalent dip lies 

 between west and north. On the south-eastern side the rocks are 

 indeed intensely folded, but the limbs of the folds are usually 

 longer and straighter, and there is less puckering ; so that, as a 

 rule, it is only in the coast-sections and in the deeper quarries that 

 the folding becomes evident ; while on the other side there is 

 presented from end to end of the Island a shorter and more intricate 

 system of folding, and a constant tendency of the shear-strain to 

 produce an actual brecciation of the bedding, especially in the 

 vicinity of masses of grit. This tendency increases very markedly 

 from south-west to north-east, being found only on a local and 

 limited scale south of the central valley which crosses the Island 

 between Douglas and Peel, but to the north of this valley rapidly 

 becoming an important element in the stratigraphy. 



(a) Coast Sections. — The most southerly occurrence of the crush- 

 structure known to me occurs in the cliffs on the western side of 

 Fleshwick Bay (see map, PI. XIX.). Here at high-water mark 

 and in the crags above, a much-folded series of sandy slates with 

 occasional layers of grit becomes locally dispersed into a mass of 

 detached fragments of grit included in a sheared slaty matrix. 



Three miles north of Pleshwick the brecciation is again met with, 

 on the foreshore under Gob Breac beyond Cronk ny Arrey Lhaa, 

 but the separated fragments are small in size, and the structure 

 not very notable. 



At the rugged reef of the Niarbyl, 1 one mile farther north, we 

 reach the southern margin 



Fig. 



2. — Crest of fold in cliff at 



northern side of The Ladder, 



Contrary Head, Peel. {Length 

 about 4 feet.) 



of a series of thin-bedded 

 slaty flags and fine-grained 

 grits, slightly calcareous 

 in places, which extends 

 thence without interruption 

 for 5 miles, until it dis- 

 appears by faulting against 

 the newer rocks (Red Sand- 

 stone and Conglomerate) at 

 Peel (see map, PI. XIX.). 

 These flags are throughout 

 magnificently plicated, and 

 show almost everywhere 

 the strain-slip cleavage and 

 other shear - structures in 

 great perfection and variety, 

 with such local discon- 

 tinuity of the bedding by 

 stretching as shown in fig. 2, 

 or by close inpacking as in 

 fig. 3 (p. 570), but otherwise they have preserved their original 

 stratification-planes. Such strata as these would, I think, if rent 



A-A. Pale band in flaggy sandy slates, 

 pulled apart into pebble-like lenticles, 

 1 to 2 inches in length. 



y, y, y. Faintly-indicated planes of strain- 

 slip. 



Pronounced Ne-ar-b v l. 



