Page:The Selkirk mountains (1912).djvu/123

Rh from which the Caves have been carved were exainined by Dr. Hoffman, Government Mineralogist, with the following pronouncement:

"A (from the Auditorium) is a light, bluish-grey, fine-crystalline, massive, non-magnesian, slightly ferruginous limestone. B (from near Entrance No. 3) is a light and dark bluish-grey, banded, fine crystalline, massive, non-magnesian, slightly ferruginous limestone. C (from the Pit) is a dark bluish-grey, fine-crystalline, massive, slightly magnesian and slightly ferruginous limestone, traversed by tortuous veinings of white (crystalline) calcite. D and E (from the white Grotto and the Judgment Hall) being samples of lime-formation on walls and ceilings, consist of a very light buff-coloured coating, having a botryuidal surface of from half an inch and less to a little over two inches in thickness, of a non-magnesia, very slightly ferruginous carbonate of lime." To ascertain their value as marbles, one surface of each crystalline sample was polished, the result showing nothing exceptional, being coarse-grained and not yielding to a very superior polish. That from the bottom of the Pit presenting a rich grey-black polished surface, shot with zig-zag streaks of crystallized calcite, was the handsomest. Thus, with a difference in colouring, the general composition of the rock is the same throughout the system.

Most of the rocks forming this portion of the Selkirks are dull white and grey quartzites and grey to greenish-grey schists. Mr. Ayres reports finding in the old channel where the Terror is situated, gravel of dark brown or red quartzite. As dark-coloured quartzites occur very rarely in this region, the brown and red tints have been the results of weathering. Pebbles and small water-worn pieces of the same material were seen within Entrance No .3, probably carried from a common source. Quartzite boulders were found in the interior of the Gorge series, doubtless brought from a distance by the subterranean flood. Outcropping from the glacier overlaying the summit of Cougar Pass may be seen a mass of almost pure white quartzite, the fragments lying about in huge rectangular blocks.

Concerning the origin of the Caves, Mr. Ayres holds that the passageways are due entirely to water-erosion owing to a small stream of Cougar Creek having found its way ages ago through a bed of limestone; and that the caverns gradually enlarged in irregular forms, through the long process of disintegration.

While holding to this theory in part, Mr. Wheeler thinks that a more potent and far-reaching agency has been at work than Nature's ordinary methods of erosion and disintegration. There is no doubt that these particular beds of limestone are badly shattered in the mass as the tributary streams bear witness: Gopher Falls, Goat Falls and a periodical stream flowing into Entrance No. 3, all join the main stream by underground ways. The rift of the Gorge lies directly across the dip of the strata, the dip being a little south of east at an angle of between 40 and 50 degrees; and the same is true of the subterranean bed of the creek from the east end of the Witches' Ball-room. When the temperature is well below zero in the valley above, there is no frost found in the caverns a short distance from the entrance. Thus, two important factors of disintegration, frost and sun, have been wanting. Moreover, the boulders already referred to are of very large size, the