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MR MILNE ON THE PARALLEL ROADS OF LOCHABER. 401 



at that point are separated by a small neck of land, — it is where there is space for 

 a considerable current on each side of the strait. 



For these reasons I consider that Mr Darwin's explanation of the coincidence 

 of the shelves ■with the water-sheds before described, is quite inadmissible. 



2. The second serious objection to Mr Darwin's theory arises from the fact, 

 that the shelves in the diflferent glens m'e not coincident in level. If they had been 

 formed by arms of the sea, as the land rose out of it, the sea should have formed 

 lines in all the valleys which it entered, at precisely the same levels. But neither 

 of the Glen Gluoy shelves is to be seen, in any of the other valleys. So also the 

 No. 2, or highest shelf of Glen Roy, and the next lowest, or No. 3, do not occur 

 In the lower part of that glen, or in the adjoining valleys of Glen Glaster, Glen 

 Spean, and Glen Treig. 



Mr Darwin attempts to explain one, but one only, of these circumstances, 

 viz., the difference of level between No. 1 and No. 2 shelves, by a theory of very 

 questionable soundness. He says, that the tide in Glen Gluoy may have risen 20 

 feet higher at the head of the estuary, than at the head of Glen Turret. It would 

 be necessary that it should rise 29 feet higher. But if this were the case, then 

 the shelves, at all events, in Glen Gluoy, would not be horizontal, or nearly so ; — 

 they would have sloped upwards towai'ds the head of Glen Gluoy, by 29 feet in 

 the course of 6 or 7 miles, — the length of the glen. But this would be inconsistent 

 with the great and weU-established fact so characteristic of these Lochaber shelves ; 

 and moreover, though the beach-lines at the heads of the two glens might not be 

 exactly coincident in level there, they ought, at all events, to be so at the mouths 

 of the glens where the supposed arms of the sea joined the main body of the ocean, — 

 which is not pretended. 



This theory, however, would explain merely the non-appearance of shelf 1 in 

 Glen Roy. The non-appearance of all the others is accounted for by Mr Darwin, 

 simply by supposing that something or other had prevented them being marked 

 in the other glens. 



In support of this view, Mr Darwin refers to two intermediate shelves which 

 are faintly traceable on Tombhran and elsewhere, in order to shew that the 

 water did produce marks at some places, and not at others. But, from the faint- 

 ness of those intermediate lines, it is manifest that the water had stood at their 

 level for a much shorter period than at the levels of the principal shelves ; and, 

 therefore, no fair inference can be drawn from the former applicable to the latter. 



3. These considerations suggest, however, a separate and even a more serious 

 objection. Not only should the sea have made markings at the same levels in all 

 the Glens of Lochaber, but it should have produced similar appeanmces, (end at 

 the same levels respectively, on all the mountains of Scotland, high enough for the 

 purpose. Mr Darwin says, " that it would be more proper to consider the pre- 

 sei-vation of these ancient beaches as the anomaly, and their obliteration from me- 

 teoric agency the ordinary course of nature." (P. 60.) Supposing him right in 



