569 



material gravitating to the bottom. An impressive illustra- 

 tion of this process will be seen by a walk up the Cathedral- 

 rock Creek to a position above the rock mentioned. 



Such abnormal conditions, occurring in the case* of a 

 hard rock with an extensive outcrop, suggest that earth 

 movements must have been particularly active and powerful 

 in bringing about such a result. This view is supported by 

 certain attendant phenomena, by which it may be possible to 

 infer the more important movements that have given outline 

 to this truly "remarkable" mount. 



1. The Great (?) Meridional Fault of the Range. 



The quartzite not only occupies the crest of the range 

 from end to end, but forms the greater part of the material 

 of which the mount is composed. The western side has a 

 more gradual slope than the eastern, probably arising from 

 the fact of its forming the dip slope of the beds, the dip 

 varying from 65° in the lower situations to about 85° on 

 the eastern side of the summit. 



When this consistently-high reading of dip is compared 

 with the great width of outcrop of these beds (reaching, as 

 already stated, at their maximum, a mile, at least, in hori- 

 zontal measurement), it must be inferred that a duplication of 

 outcrop has occurred that has greatly increased the surface 

 spread of the stone and given a fictitious appearance as to its 

 true width. 



What has happened to produce this remarkable thicken- 

 ing of the quartzite forming the axis of the mount is not at 

 all clear. Various tectonic movements, under certain con- 

 ditions, might lead to such a result, as, for example, in the 

 following Cases : — 



(a) An unconformity, with the quartzite (as the upper 

 series) forming a cap, with the beds inclined at a 

 low angle, as shown by Selwyn (loc. cit.J. But 

 Selwyn's geological section of the mount is entirely 

 in error; there is no unconformable series, there 

 are no underlying slates (as shown by Selwyn), 

 and the quartzite, instead of dipping at a low 

 angle (as shown by Selwyn), dips at a high angle 

 and is interbedded with the other beds of the 

 section. 

 (b ) A double monoclinal-fold, or "hogback," with 

 faulting in the septum curves on each side of the 

 upthrow, and the arch worn down to the level of 

 the resisting quartzite, might give a great breadth 

 to the latter bed ; but this explanation is not 



