36 ON THE PARALLEL ROADS 



surface sinks suddenly into Glen Gluoy. In order to have 

 something like an approximation to the truth, as to what dif- 

 ference of level subsisted between Shelf 1st in Glen Gluoy, 

 and Shelf 2d in Glen Turret, I travelled from the cascade up- 

 wards, through the High Glen, measuring as nearly as I could 

 by the eye, and adding together, all the little falls of the 

 stream, guessing at the addition, and subsequent deduction to 

 be made at the end next Glen Gluoy : the result which I had 

 from this rude process was fourteen or fifteen feet. In order to 

 make certain however, of a point which I considered most ma- 

 terial, I requested the favour of my friend Mr Maclean to re- 

 visit the ground, for the purpose of levelling it properly by 

 means of the instrument ; he was so kind as to indulge me, and 

 the twelve feet of difference of level in the height of Shelf 1st 

 above Shelf 2d, is given as the result of his observations. 

 Such, therefore, is the nature of the levels here, that suppo- 

 sing Glen Gluoy to be filled with a body of water to a height 

 equal to that of its shelf, and that, at the same time, the thick 

 stratum of moss were to be removed, the consequence would 

 be, that a stream would be discharged from it by the High 

 Glen, and over the cascade into Glen Turret, and so into Glen 

 Roy. 



Let us now return to the head of Lower Glen Roy, where 

 Shelf 3d and Shelf 2d, having wound from the ravine on the 

 south side of the isolated rock, run faintly down the faces of 

 the mountains on the south-west side of the glen, gaining 

 greater distinctness of form as they proceed. They become 

 particularly well defined, just at^in the map, where they sub- 

 tend the mouth of Glen Turret j and in that part of the south 

 side of the valley, there are appearances which may be worth 

 notice. At first sight, one might be led to imagine, that there 

 are no fewer than seven different stages of shelves here. A 

 sketch could have given no idea of these ; but the diagram, 



(Plate VII. 



