DESCRIPTIVE GEOLOGY: GENERAL CONSIDERATIONS. 263 



it is incalculably greater in the latter than in the former. Thus the 

 sone that indicated the greatest elevation exhibits also the greatest 

 compression and vice versa. 



Between zone A and zone B, though we might not be able to 

 trace out contrasting amounts in the coarser effects or larger foldings 

 of the strata, yet, descending to the minuter structure of the rocks, 

 we must at once be made aware of the marked way in which zone 

 A has yielded to compression in this respect as compared with zone 

 B. What were slates originally in A have become divided through 

 and through by a completely new set of foliation planes along which 

 a fresh mineralization has taken place ; what was an ordinary con- 

 glomerate (the Infra-Trias) composed of great blocks and boulders 

 oriented in any way in a fine shaley matrix has become a slate t or a 

 faintly glistening schist. In some extreme cases as we have seen 

 (p. 55) earth movements with compression have acted on this 

 easily-traced rock to such an extent that the flattened and drawn-out 

 pebbles would with difficulty be recognised did not stratigraphical 

 evidence point conclusively to its former condition. As regards the 

 coarse sandstones and limestones belonging to the same epoch, zone 

 A tells a similar tale of differential movements of the minuter par- 

 ticles of the rocks, specimens from which at Bilihana mountain and 

 the Gundgurh have been particularly described (Chapter I, pages 56, 



57)- 



But though these effects of compression vary greatly in zone A, 



they are absent or very nearly absent in zone B ; and though in 

 the Gundgurh hills and near Gurhee-Hubeebooluh there are signs of 

 a gradual passage from the slates to the metamorphic schists, the line 

 of change, albeit a gradual one, is extremely well-marked and shows 

 no fluctuations on either side, that is to say, no recurrence or inter- 

 beddings of metamorphic rocks with non-metamorphic rocks. In 

 other words, the change from the Slate zone B to the Metamorphic 

 zone A, though gradual, is rapid and irrevocable. 



I do not think I need urge more proofs to establish the statement 

 that zone A, which showed a greater general elevation than zone 



( 263 ) 



