312 GEOLOGICAL APPEARANCES 



angles to the direction of the valley, and therefore also at right 

 angles to the stretch of the strata. 



22. One of these lines was in the course of a brook, which 

 falls down the mountain within a quarter of a mile to the east- 

 ward of the point A, and has made a deep section of the rock, 

 though not in the immediate vicinity of the river, where the 

 declivity is gentle. After passing over this declivity, I found 

 granular limestone and mica-slate, from where the rock first 

 appears, to the height of about two hundred feet above the ri- 

 ver. For the next two or three hundred feet, there followed 

 a gneiss, resembling that which I have already mentioned as 

 occurring near Blair, on the western side of the Tilt. It is 

 rarely stratified in its texture, and its stratification can only be 

 learned from the outgoings of its large beds. These, as well 

 as the limestone and mica-slate below them, dip into the 

 mountain to the south-east, at an angle sometimes considera- 

 bly more than 45°, and sometimes a little less. To the 

 gneiss succeeds mica-slate, conformably stratified ; and to that, 

 another gneiss, a good deal similar in its texture to the last. 

 Its beds are crossed by numerous slaty fissures, at right angles 

 to their planes, which give it the delusive appearance of a stra- 

 tification dipping at right angles to that of the rocks below ; 

 while, in fact, the beds lie conformably. Above, are distinct 

 strata of granular quartz, also conformable. This quartz was 

 the highest rock that I examined, and might be about six hun- 

 dred feet above the river. About a quarter of a mile farther 

 to the eastward, the strata are intersected by another brook ; 

 and, as far as I could judge from a distant view, they corres- 

 pond with those in the first, as to the limestone, and the lower 

 beds of gneiss. 



23. The other line, in which the rock was examined, on this 

 side of the valley, sets off from the Tilt, at a bridge near half a 



mile 



