i540 Mr Milne on the Parallel Boads of Lochaber. 



shelves which mark the mountain sides of these valleys, that thoy 

 had been occupied by lakes, which, by earthquakes or other violent 

 convulsions, had been drained. This theory was generally received, 

 until, in the year 1839, Mr Darwin, so justly celebrated as a geolo- 

 gist, and an accurate observer, published his views, and pronounced 

 the shelves to have been formed by the sea ; an opinion which, bo- 

 sides being rested on proofs derived from the locality, he enforced 

 also by his observation of similar appearances in South America. 



Mr Darwin's opinion has received the assent of Sir Roderick I. 

 Murchison, Mr Lyell, and Mr Horner, all successively Presidents of 

 the Geological Society, besides other geologists, both at home and 

 abroad, who are justly regarded as authorities in physical science. 

 Relying on the soundness of their views, I confess that when I went 

 to Glen Roy, in the year 1845, it was with a strong conviction that 

 the lake theory was indefensible ; a view to which I was the more in- 

 clined, from having studied certain marks along different parts of 

 the Scottish coast, on both sides of the island, which satisfied me 

 that the sea had recently stood at a much higher relative level than 

 at present ; and that, in its recession, it had formed, all round our 

 coasts, shelves or beach lines, very analogous to those in the Loch- 

 aber valleys. I had not been two days in Glen Roy, before I satis- 

 fied myself that these views were inapplicable to the shelves in it 

 and its associated valleys. But I was unable during my visit of 

 1845, to remain long enough to obtain evidence of the manner in 

 which the lakes had been dammed up, and eventually drained. I there- 

 fore resolved to defer the farther consideration of the subject, until I 

 could pay a second visit. This I accomplished in September 1846, 

 when I spent a week in the examination. 



In the following paper, I shall attempt to explain my reasons for 

 thinking Mr Darwin's theory inadmissible, and to point out the 

 manner in which, as it appears to me, the lakes were drained, — 

 not as supposed by Dr MacCulloch and Sir Thomas Dick Lauder, by 

 convulsions of nature, but by the gradual operation of ordinary causes. 



Though it is the principal object of this paper to account for the 

 formation of the Lochaber shelves, there are no views regarding them 

 which can be suggested, which have not a more general bearing, and 

 the soundness of which may be tested by evidence supplied from 

 other sources. Former writers, accordingly, and especially Mr Dar- 

 win, have felt it to be necessary, after giving their explanation of 

 the parallel roads, to shew, that the principles on which it rests, arc, 

 at least, not inconsistent with any established truths in other 

 branches of geology. 



I shall not shrink from subjecting the Lake theory, which I have 

 to submit, to a similar ordeal ; and the more so, as I feel satisfied 

 that it receives great support from geological considerations now 

 held to be well established. 



As the whole details of the parallel roads have been fully de- 



