Recent Formations. 105 



In this case the shdiug clay had carried pieces of the roof towards the 

 valley. 



"Of all common minerals only quartz can withstand this cumulative 

 decomposition ; quartz I'eefs, therefore, come up to the surface in the 

 measure as their thickness and their cohesion increase. The four-foot reef 

 of the Kanaimapoo mine on the Demerara can be traced on the surface 

 for quite a distance, and the Blue reef in the Garnett Syndicate, on 

 Ti,<i:er Creek, can at several places be seen right in the placer workings. 

 All others of less magnitude or cohesion are shattered, and their sharp- 

 edged pieces are carried to the valley. These clays, during the process 

 of sliding, shrink as the water drains from them, and it is for this 

 reason that the outcrop of the vein in Anderson Creek appeared at the 

 surface only after it had travelled a distance of some 160 feet." 



I have seen several instances of similar movemc^nts in the North- 

 western district, and some of them were described in the report by 

 Perkins and myself on the gold fields of that district, published in 

 1897. In the following paragraph we ascribed the numerous small 

 faults which we had noticed in the cjuartz reefs to the same cause : — 



" The small faults, in our opinion, are of purely local origin, due in 

 part to the alteration in volume of the underlying rocks by progressive 

 hydration, oxidation, and decomposition, and in part to slips and slides 

 on the hillsides." 



Near the Winter mine in the Arakaka district there is a section in 

 which, on the sl(jpe of a hill, a quartz vein has been inverted and more 

 or less shattered, so that the portion of it higher on the hillside overlaid 

 that lower down, apparentl}' having been jDushed forward, and inverted 

 in the process. This was probably due to the slipping of the residual 

 deposits of which the hill consisted, in the manner described in the 

 above quotation from Dr. Lungwitz's article. 



