Mr Milne on tlie Parallel Beads of LocJiaber. 343 



In like manner, the only shelf which occurs in Glen Spean, No. 4 

 in Sir Thomas Dick Lauder's Memoir, is exactly coincident with, or 

 rather is a few feet above, the pass of Mukkul at the head of Loch 

 Laggan, through which pass, the waters standing at the level of No. 

 4 must have flowed eastward into Spey valley. These coincidences, 

 as Mr Darwin admits, *' are so remarkable, that they must (I use 

 his own words) be intimately connected with the origin of the 

 shelves ; although such relation is not absolutely necessary, inas- 

 much as the middle shelf of Glen Roy is not on a level with any 

 watershed:* (P. 43.) 



The middle shelf here alluded to is No. 3 in Sir Thomas Dick 

 Lauder's list. The discovery which I made, was its exact coinci- 

 dence with a water-shed at the head of Glen Glaster, a glen which, 

 though branching up from Glen Roy near the bottom of it, oddly 

 enough does not appear to have been visited, and certainly not to 

 have been described, by any former observer. 



Shelves 3 and 4 are the only shelves which enter and run up this 

 glen. Sir Thomas Dick Lauder's map inaccurately represents shelf 

 2 as marking it on both its sides. Shelf 2 stops, however, on both 

 sides of Glen Roy a little to the eastward of, or above the mouth of 

 Glen Glaster. 



In following shelf 3 to the head of this glen, I found that it was 

 there lost in a low mossy flat. A little beyond this flat, and a few 

 feet below the summit-level, an old river-course can be distinctly 

 traced down a slope towards Loch Laggan. It has a rocky bed, 

 over which a great body of water had evidently flowed at some 

 former period. The breadth of the rocky bed is from 30 to 40 

 feet ; the knolls of rock are from 2 to 5 feet high, and amongst 

 them are rounded blocks of stone, such as occur in all great High- 

 land rivers. I traced this rocky channel for about a mile towards 

 Loch Laggan ; and I afterwai'ds found the place where it had dis- 

 charged its waters into Loch Laggan, when that loch stood at shelf 

 4. It is marked by a huge delta, forming a projecting buttress at 

 the level of that shelf, and bulging far beyond the general side of 

 the Laggan valley. 



On examining the rocky knolls attentively in this ancient river- 

 course, I found that the smooth faces were all towards Glen Glaster, 

 and the rough faces in the opposite direction, affording proof, if 

 such were needed, that the stream which flowed there had come 

 from Glen Glaster. 



A small rivulet trickles now among the rocks, infinitely too feeble 

 to have produced the appearances. 



It is now, therefore, established, not only that the whole of the 

 4 shelves of Lochaber are coincident with water-sheds respec- 

 tively, but that a great body of water had filled Glen Glaster, and 

 of course Glenroy, the outlet of which was down this ancient rover- 



