350 THE JOURNAL OF GEOLOGY. 



cores being plainly visible. They, however, often show wavy 

 extinction and even cracks, but not to a greater degree than the 

 grains in the massive quartzite ; for in the latter the full stress of 

 the pressure has been borne by the grains in full touch, not 

 separated by a plastic matrix, as are the grains of quartz in the 

 argillaceous layers. In the matrix of the schist are numerous 

 small flakes of muscovite, arranged with their longer axes in 

 a common direction, much finely crystalline quartz, and a good 

 deal of iron oxide. 



It is concluded that the clayey character of the beds, and, 

 consequently, the greater ease of movement within them, has 

 located the slipping - planes and shear - zones, necessary in order to 

 accommodate the beds to their new positions. On the south range, 

 near Devil's Lake, these shear -zones are generally not more than 

 six or eight inches wide. They may be well seen just back of 

 the Cliff House, and on the Northwestern Railway, about one-half 

 mile south of this house. All of these shear -zones are parallel 

 with the bedding, and illustrate the possibility, so far as I know 

 first mentioned by H. L. Smyth, that a crystalline schist, with 

 schistosity parallel to bedding, may be produced by shearing 

 along the bedding- planes. 



On the railroad track, near the locality where these shear - 

 zones may be seen, is also an almost vertical shear -zone, two to 

 four feet wide. It therefore cuts almost directly across the beds 

 of quartzite, which here incline to the south about twelve or 

 thirteen degrees. Throughout this band, the quartzite is broken 

 into angular trapezoidal fragments, the longer directions of which 

 are vertical, and which may be picked out with the hammer. In 

 certain parts of the zone well-defined gruss or friction cla)^ 

 produced by the grinding of the fragments against one another, 

 has been produced. This is clearly a plane of faulting. How 

 much the throw of this fault is it is not easy to say, as the heavy 

 beds of quartzite are so similar that it is impossible to certainly 

 identify them. At this place there is, however, a change in the 

 character of the quartzite, layers of light color being overlain by 

 other beds, which are more heavily stained with iron oxide. This 



