Mr Milne 07i the Parallel Boads of Lochaber, 347 



Iiavo produced similar appearances, and at the same levels respec- 

 tively, on all the mountains in Scotland, high enough for the pur- 

 pose. Mr Darwin says, ** that it would be more proper to consider 

 the preservation of those ancient beaches as the anomaly, and their 

 obliteration from meteoric agency the ordinary course of nature." 

 (P. 60.) Supposing him right in this, he ought to have shewn how 

 circumstances caused that anomaly at Glen Roy and its adjoining 

 vafleys. But he has not shewn, and cannot shew, that the sides of 

 the Glen Roy mountains, are in any respect different from those 

 other highland mountains. Indeed, he has himself pointed out a 

 similar beach lino at Kilfinnin, in a glen towards Inverness. I 

 take leave farther to doubt the soundness of Mr Darwin's proposition, 

 that the preservation of ancient beach lines is anomalous. The 

 whole of Scotland, and I believe also of the British Islands, is begirt 

 with lines of ancient sea beach. 



4. The ancient sea beaches, now alluded to as existing along our 

 coasts, present a very marked contrast with the Lochaber shelves. 

 If these shelves had been formed by the sea, it will, I presume, be 

 admitted that, considering their great altitude, they are of much 

 older date than beach lines at a lower level. If older, then they 

 shoidd he less perfect and entire. But the contrary is the case. 

 They are incomparably more perfect and entire than any of the 

 lowest ancient sea terraces which occur along our coasts. 



6. If the Lochaber roads were formed by the sea, the well-known 

 action of the tides, to which Mr Darwin refers, would have prC" 

 eluded the formation of them along lines absolutely horizontal. 



Mr Darwin refers to a case in South America, where, in 18 

 miles, the tidal wave rises at one place 20 feet higher than another 

 in the same estuary. Nearer home, in the Bristol Channel, the 

 sea rises at its head about 60 feet hicrher than at its mouth. 



o 



The tide at Blackwall rises 12 feet higher than at Yarmouth. 

 In the Frith of Tay, the tide rises at Perth 18 inches above the 

 level at Newburgh. The tide at Alloa is said to rise 2 feet 9 inches 

 above its level at Leith. At Glasgow, the tide rises 10 or 11 inches 

 above its level at Greenock. On the Dee, the level of high water is, 

 at Chester, 8 inches above what it is at Flint, near the mouth of the 

 river, a distance of 1 1 miles. 



On this principle, the beaches of Lochaber, if formed by arms of 

 the sea, ought all gradually to rise to the head of the Glens — narrow- 

 ing, as these glens do, towards the head. But this is negatived by 

 the fact. 



6. On more narrowly considering the effect of tidal action, it will 

 readily occur, that the beaches formed by the sea must be materally 

 different from those of a lakcy in which there is no movement of the 

 water at the sides, except such as is caused by winds common to both. 

 In the case of the sea, there is not only a vortical rise and fall of 

 water (which, on the west coast of Scotland, is from 8 to 16 hti) 



