24 ON THE PARALLEL ROADS 



into it from tli e side of the mountain Ben-y-vaan, guarding its en- 

 trance on the south,— traversed its whole extent, going up the one 

 side of the river, and down the other, so as to endeavour to se- 

 cure the most perfect view of the two corresponding parts of 

 the shelf, — and looked down its whole length, from a point on 

 the side of the mountains, at its upper extremity, (see a in the 

 map), whence an excellent view of it is enjoyed, (see Plate I.) 

 About three miles up Glen Gluoy, it is joined by a smaller 

 valley, called Glen Fintackj whence a considerable stream, ha- 

 ving a short run, pours itself into the Gluoy. Above this, the 

 glen makes several gentle winds. Shelf Is/, the only one to 

 be met with in Glen Gluoy, first appears near the top of the 

 mountain, on the N. W. side of the valley, a considerable way 

 below that part of it which is opposite to Glen Fintack. The 

 sides of Ben-y-vaan, which is a long flat-ridged mountain, are 

 rocky ; and the whole sides of Glen Fintack are particular- 

 ly so, presenting every where a very magnificent enclosure, of 

 abrupt and perpendicular precipices of great height. I could 

 not perceive any appearance of the shelf on the S. E. side, un- 

 til I observed it on the face of the mountain which bends out 

 from the N. E. side of Glen Fintack, into Glen Gluoy. At 

 this point there even appears to be some traces of two lines ; 

 but one of these, I believe the uppermost, is not continued, 

 and is probably nothing more than an accidental mark on the 

 angle of the hill. And here I may take the opportunity of of- 

 fering a caution to future observers, not to decide too hastily 

 as to such faint appearances, unless in situations where the 

 probability of their being portions of the shelf is borne out by 

 a sameness of level. For, aided by fancy, which is always 

 alive in an investigation of this kind, the eye is very apt to 

 lead the judgment into error. I may mention, as one very 

 strong instance of this, that, at one place, on the N. W. side, 

 and nearer to the upper end of Glen Gluoy, I was for some 



time 



